Arlington County, or simply Arlington, is a county in the U.S. state of Virginia. The county is located in Northern Virginia on the southwestern bank of the Potomac River directly across from Washington, D.C., the national capital.

Arlington County is coextensive with the U.S. Census Bureau's census-designated place of Arlington. Arlington County is the eighth-most populous county in the Washington metropolitan area with a population of 238,643 as of the 2020 census. If Arlington County were incorporated as a city, it would rank as the third-most populous city in the state. With a land area of 26 square miles (67 km2), Arlington County is the geographically smallest self-governing county in the nation.

Arlington County is home to the Pentagon, the world's second-largest office structure, which houses the headquarters of the U.S. Department of Defense. Other notable locations are DARPA, the Drug Enforcement Administration's headquarters, Reagan National Airport, and Arlington National Cemetery. Colleges and universities in the county include Marymount University and George Mason University's Antonin Scalia Law School, School of Business, the Carter School for Peace and Conflict Resolution, and Schar School of Policy and Government. Graduate programs, research, and non-traditional student education centers affiliated with the University of Virginia and Virginia Tech are also located in the county.

Corporations based in the county include the co-headquarters of Amazon, several consulting firms, and the global headquarters of Boeing, Raytheon Technologies, and BAE Systems Platforms & Services.

Present-day Arlington County was part of Fairfax County in the Colony of Virginia during the colonial era. Land grants from the British Crown were awarded to prominent Englishmen in exchange for political favors and efforts as part of the county's early development. One of the grantees was Thomas Fairfax for whom both Fairfax County and the City of Fairfax are named. The county's name was derived from Henry Bennet, the Earl of Arlington, which was a plantation along the Potomac River, and Arlington House, the family residence on that property. George Washington Parke Custis, grandson of First Lady Martha Washington, acquired the land in 1802. The estate was later passed down to Mary Anna Custis Lee, wife of Robert E. Lee, a Confederate general during the American Civil War, and then later seized by the U.S. federal government in a tax sale. The property later became the Arlington National Cemetery.

Present-day Arlington County and most of present-day Alexandria were ceded to the new federal government by Virginia. On July 16, 1790, the Congress passed the Residence Act, which authorized the relocation of the capital from Philadelphia to a location to be selected on the Potomac River by U.S. President George Washington. The Residence Act originally only allowed the President to select a location in Maryland as far east as the Anacostia River. President Washington, however, shifted the federal territory's borders to the southeast in order to include the existing town of Alexandria.

In 1791, Congress, at Washington's request, amended the Residence Act to approve the new site, including the territory ceded by Virginia. The amendment to the Residence Act prohibited the "erection of the public buildings otherwise than on the Maryland side of the River Potomac."

The initial shape of the federal district was a square, measuring 10 miles (16 km) on each side, totaling 100 square miles (260 km2). In 1791 and 1792, Andrew Ellicott and several assistants placed boundary stones at every mile point. Fourteen of these markers were in Virginia, and many of the stones are still standing.

When Congress arrived in the new capital from Philadelphia, one of their first acts was to pass the Organic Act of 1801, officially organizing the District of Columbia and placing the entire federal territory, including present-day Washington, D.C., Georgetown, and Alexandria under the exclusive control of Congress. The territory in the District was organized into two counties: the County of Washington to the east of the Potomac River and the County of Alexandria to the west. It included almost all of present-day Arlington County and part of present-day Alexandria.

The Act established the borders of the area that eventually became Arlington, but the citizens in Washington, D.C., were no longer considered residents of Maryland or Virginia, which represented the end of their federal representation in Congress.

Prior to retrocession, residents of Alexandria County expected the proximity of the federal capital to result in higher land prices and the growth of regional commerce. The county instead found itself struggling to compete with the Chesapeake and Ohio Canal in Georgetown, which was farther inland and on the northern side of the Potomac River next to Washington, D.C. Members of Congress from other areas of Virginia used their influence to prohibit funding for projects, including the Alexandria Canal, which would have increased competition with their home districts. Congress also prohibited the federal government from establishing any offices in Alexandria, which made the county less important to the functioning of the national government.

Alexandria was a center for the slave trade; Franklin and Armfield Office in Alexandria was once an office used in slave trading. Rumors circulated that abolitionists in Congress were attempting to end slavery in the District, an act that, at the time, would have further depressed Alexandria's slavery-based economy. At the same time, an active abolitionist movement arose in Virginia that created a division on the question of slavery in the Virginia General Assembly. Pro-slavery Virginians recognized that if Alexandria were returned to Virginia, it could provide two new representatives who favored slavery in the state legislature. Some time after retrocession, during the American Civil War, this division led to the formation of West Virginia as a state, which comprised what then 51 counties in the northwest part of the state that favored abolitionism.

Largely as a result of the economic neglect by Congress, divisions over slavery, and the lack of voting rights for the residents of the District, a movement grew to return Alexandria to Virginia from the District of Columbia. From 1840 to 1846, Alexandrians petitioned Congress and the Virginia legislature to approve such a transfer, known as retrocession. On February 3, 1846, the Virginia General Assembly agreed to accept the retrocession of Alexandria if Congress approved. Following additional lobbying by Alexandrians, Congress passed legislation on July 9, 1846, to return all the District's territory south of the Potomac River back to Virginia, pursuant to a referendum, and President James K. Polk signed the legislation the next day. A referendum on retrocession was held on September 1 and 2, 1846, and the voters in Alexandria voted in favor of the retrocession by a margin of 734 to 116, while those in the rest of Alexandria County voted against retrocession 106 to 29. Pursuant to the referendum, President Polk issued a proclamation of transfer on September 7, 1846. However, the Virginia legislature did not immediately accept the retrocession offer. Virginia legislators were concerned that Alexandria County residents had not been properly included in the retrocession proceedings. After months of debate, on March 13, 1847, the Virginia General Assembly voted to formally accept the retrocession legislation.

In 1852, the Virginia legislature voted to incorporate a portion of Alexandria County as the City of Alexandria, which until then had been administered only as an unincorporated town within the political boundaries of Alexandria County.

During the American Civil War, Virginia seceded from the Union following a statewide referendum on May 23, 1861; the voters from Alexandria County approved secession by a vote of 958–48. The vote indicates the degree to which its only town, Alexandria, was pro-secession and pro-Confederate. Rural county residents outside Alexandria were largely Union loyalists and voted against secession.

For the duration of the Civil War, the Confederacy claimed the whole of antebellum Virginia, including the more staunchly Union-supporting northwestern counties that eventually broke away and were later admitted to the Union in 1863 as West Virginia. However, the Confederacy never fully controlled all of present-day Northern Virginia. In 1862, the U.S. Congress passed a law that required that obligated owners of property in districts where active Confederate insurrections were occurring to pay their real estate taxes in person.

In 1864, during the Civil War, the U.S. federal government confiscated the Abingdon estate, which was located on and near the present Ronald Reagan Washington National Airport, when its owner failed to pay the estate's property tax in person because he was serving in the Confederate States Army. The government then sold the property at auction, and the purchaser leased the property to a third party.

In 1865, after the Civil War ended, the Abingdon estate's heir, Alexander Hunter, filed a federal lawsuit to recover the property. James A. Garfield, a Republican member of the U.S. House of Representatives who was a brigadier general in the Union Army during the Civil War and later became the 20th President of the United States, was an attorney on Hunter's legal team. In 1870, the U.S. Supreme Court found that the U.S. federal government had illegally confiscated the property and ordered that it be returned to Hunter.

The property included the former residence of Confederate General Robert E. Lee's family at and around Arlington House, which had been subjected to an appraisal of $26,810, on which a real estate tax of $92.07 was assessed. Likely fearing an encounter with Union officials, Lee's wife, Mary Anna Custis Lee, the owner of the property, chose not pay the tax in person. She instead sent an agent on her behalf, but Union officials refused to accept it. As a result of the 1862 law, the U.S. federal government confiscated the property, and transformed it into a military cemetery.

After the Civil War ended and his parents died, George Washington Custis Lee, the Lees' eldest son, initiated a federal legal action in an attempt to recover the property. In December 1882, the U.S. Supreme Court found that the U.S. federal government illegally confiscated the property without due process, and the property was returned to Custis Lee. In 1883, the U.S. Congress purchased the property from Lee for its fair market value of $150,000, whereupon the property became a military reservation and eventually Arlington National Cemetery. Although Arlington House is within the National Cemetery, the National Park Service presently administers the House and its grounds as a memorial to Robert E. Lee.

Confederate incursions from Falls Church, Minor's Hill and Upton's Hill, then securely in Confederate hands, occurred as far east as the present-day Ballston. On August 17, 1861, 600 Confederate soldiers engaged the 23rd New York Infantry Regiment near Ballston, killing a Union Army soldier. Later that month, on August 27, another large incursion of 600 to 800 Confederate soldiers clashed with Union soldiers at Ball's Crossroads, Hall's Hill, and at the present-day border between the Falls Church and Arlington. A number of soldiers on both sides were killed. However, the territory in present-day Arlington never fell under Confederate control and was not attacked.

In 1870, the City of Alexandria was legally separated from Alexandria County by an amendment to the Virginia Constitution that made all Virginia incorporated cities (though not incorporated towns) independent of the counties with which they had previously been a part. Confusion between the city and the county of Alexandria having the same name led to a movement to rename Alexandria County.

In 1896, an electric trolley line was built from Washington, D.C. through Ballston; Northern Virginia trolleys were a significant factor in the county's growth. In 1920, the trolley was named Arlington County, named after Arlington House, the home of the American Civil War Confederate general Robert E. Lee later seized by the Union in a tax sale, is located on the grounds of Arlington National Cemetery.

In 1900, Blacks were more than a third of Arlington County's population. Over the course of the century, the Black population dwindled. Neighborhoods in Arlington set up racial covenants and forbade Blacks from owning or domiciling property. In 1938, Arlington banned row houses, a type of housing that was heavily used by Black residents. By October 1942, not a single rental unit was available in the county. In the 1940s, the federal government evicted black neighborhoods to build the Pentagon and make room for highway construction.

In 1908, Potomac was incorporated as a town in Alexandria County, and was annexed by Alexandria in 1930.

In 1920, the Virginia legislature renamed the area Arlington County to avoid confusion with the City of Alexandria which had become an independent city in 1870 under the new Virginia Constitution adopted after the Civil War.

In the 1930s, Hoover Field was established on the present site of the Pentagon; in that decade, Buckingham, Colonial Village, and other apartment communities also opened. World War II brought a boom to the county, but one that could not be met by new construction due to rationing imposed by the war effort.

In October 1949, the University of Virginia in Charlottesville created an extension center in the county named Northern Virginia University Center of the University of Virginia. This campus was subsequently renamed University College, then the Northern Virginia Branch of the University of Virginia, then George Mason College of the University of Virginia, and finally to its present name, George Mason University. The Henry G. Shirley Highway, also known as Interstate 395, was constructed during World War II, along with adjacent developments such as Shirlington, Fairlington, and Parkfairfax.

In February 1959, Arlington Public Schools desegregated racially at Stratford Junior High School, which is now Dorothy Hamm Middle School, with the admission of black pupils Donald Deskins, Michael Jones, Lance Newman, and Gloria Thompson. The U.S. Supreme Court's ruling in 1954, Brown v. Board of Education of Topeka, Kansas had struck down the previous ruling on racial segregation Plessy v. Ferguson that held that facilities could be racially "separate but equal". Brown v. Board of Education ruled that "racially separate educational facilities were inherently unequal". The elected Arlington County School Board presumed that the state would defer to localities and in January 1956 announced plans to integrate Arlington schools.

The state responded by suspending the county's right to an elected school board. The Arlington County Board, the ruling body for the county, appointed segregationists to the school board and blocked plans for desegregation. Lawyers for the local chapter of the National Association for the Advancement of Colored People (NAACP) filed suit on behalf of a group of parents of both white and black students to end segregation. Black pupils were still denied admission to white schools, but the lawsuit went before the U.S. District Court, which ruled that Arlington schools were to be desegregated by the 1958–59 academic year. In January 1959 both the U.S. District Court and the Virginia Supreme Court had ruled against Virginia's massive resistance movement, which opposed racial integration. The Arlington County Central Library's collections include written materials as well as accounts in its Oral History Project of the desegregation struggle in the county.

During the 1960s, Arlington experienced challenges related to a large influx of newcomers during the 1950s. M.T. Broyhill & Sons Corporation was at the forefront of building the new communities for these newcomers, which would lead to the election of Joel Broyhill as the representative of Virginia's 10th congressional district for 11 terms. The old commercial districts did not have ample off-street parking and many shoppers were taking their business to new commercial centers, such as Parkington and Seven Corners. Suburbs further out in Virginia and Maryland were expanding, and Arlington's main commercial center in Clarendon was declining, similar to what happened in other downtown centers. With the growth of these other suburbs, some planners and politicians pushed for highway expansion. The Federal Aid Highway Act of 1956 would have enabled that expansion in Arlington. The administrator of the National Capital Transportation Agency, economist C. Darwin Stolzenbach, saw the benefits of rapid transit for the region and oversaw plans for a below ground rapid transit system, now the Washington Metro, which included two lines in Arlington. Initial plans called for what became the Orange Line to parallel I-66, which would have mainly benefited Fairfax County.

Arlington County officials called for the stations in Arlington to be placed along the decaying commercial corridor between Rosslyn and Ballston that included Clarendon. A new regional transportation planning entity was formed, the Washington Metropolitan Transit Authority. Arlington officials renewed their push for a route that benefited the commercial corridor along Wilson Boulevard, which prevailed. There were neighborhood concerns that there would be high-density development along the corridor that would disrupt the character of old neighborhoods.

With the population in the county declining, political leaders saw economic development as a long-range benefit. Citizen input and county planners came up with a workable compromise, with some limits on development. The two lines in Arlington were inaugurated in 1977. The Orange Line's creation was more problematic than the Blue Line's. The Blue Line served the Pentagon and National Airport and boosted the commercial development of Crystal City and Pentagon City. Property values along the Metro lines increased significantly for both residential and commercial property. The ensuing gentrification caused the mostly working and lower middle class white Southern residents to either be priced out of rent or in some cases sell their homes. This permanently changed the character of the city, and ultimately resulted in the virtual eradication of this group over the coming 30 years, being replaced with an increasing presence of a white-collar transplant population mostly of Northern stock.

While a population of white-collar government transplant workers had always been present in the county, particularly in its far northern areas and in Lyon Village, the 1980s, 1990s and 2000s saw the complete dominance of this group over the majority of Arlington's residential neighborhoods, and mostly economically eliminated the former working-class residents of areas such as Cherrydale, Lyon Park, Rosslyn, Virginia Square, Claremont, and Arlington Forest, among other neighborhoods. The transformation of Clarendon is particularly striking. This neighborhood, a downtown shopping area, fell into decay. It became home to a vibrant Vietnamese business community in the 1970s and 1980s known as Little Saigon. It has now been significantly gentrified. Its Vietnamese population is now barely visible, except for several holdout businesses. Arlington's careful planning for the Metro has transformed the county and has become a model revitalization for older suburbs.

In 1965, after years of negotiations, Arlington swapped some land in the south end with Alexandria, though less than originally planned. The land was located along King Street and Four Mile Run. The exchange allowed the two jurisdictions to straighten out the boundary and helped highway and sewer projects to go forward. It moved into Arlington several acres of land to the south of the old county line that had not been a part of the District of Columbia.

On September 11, 2001, five al-Qaeda hijackers deliberately crashed American Airlines Flight 77 into the Pentagon, killing 115 Pentagon employees and 10 contractors in the building, and all 53 passengers, six crew members, and five hijackers on board the aircraft. The coordinated attacks were the most deadly terrorist attack in world history.

In 2009, Turnberry Tower, located in the Rosslyn neighborhood, was completed. At the time of completion, the Turnberry Tower was the tallest residential building in the Washington metropolitan area.

In 2017, Nestlé USA chose 1812 N Moore in Rosslyn as their U.S. headquarters.

In 2018, Amazon.com, Inc. announced that it would build its co-headquarters in the Crystal City neighborhood, anchoring a broader area of Arlington and Alexandria that was simultaneously rebranded as National Landing.

By 2020, single-family detached homes accounted for nearly 75% of zoned property in Arlington.

In 2023, the Arlington County city council unanimously approved a modest zoning change to permit sixplexes (so-called "missing middle" housing) on lots previously zoned exclusively for single-family homes. The change reversed exclusionary zoning laws that were initially erected to keep low-income people and minorities out of the county. In 2024, Arlington County circuit court judge David Schell overturned this zoning change after a small group of NIMBY homeowners filed a lawsuit against the county. Schell ruled that Arlington County did not study the potential impacts adequately.

Arlington County is located in Northern Virginia and is surrounded by Fairfax County and Falls Church to the west, the city of Alexandria to the southeast, and the national capital of Washington, D.C. to the northeast across the Potomac River, which forms the county's northern border. Minor's Hill and Upton's Hill represent the county's western borders.

According to the U.S. Census Bureau, the county has a total area of 26.1 square miles (67.6 km2), 26.0 square miles (67.3 km2) of which is land and 0.1 square miles (0.3 km2) (0.4%) of which is water. It is the smallest county by area in Virginia and is the smallest self-governing county in the United States. About 4.6 square miles (11.9 km2) (17.6%) of the county is federal property. The county courthouse and most government offices are located in the Courthouse neighborhood.

Since the late 20th century, the county government has pursued a development strategy of concentrating much of its new development near transit facilities, such as Metrorail stations and the high-volume bus lines of Columbia Pike. Within the transit areas, the government has a policy of encouraging mixed-use and pedestrian- and transit-oriented development. Some of these "urban village" communities include:

In 2002, Arlington received the EPA's National Award for Smart Growth Achievement for "Overall Excellence in Smart Growth." In 2005, the County implemented an affordable housing ordinance that requires most developers to contribute significant affordable housing resources, either in units or through a cash contribution, in order to obtain the highest allowable amounts of increased building density in new development projects, most of which are planned near Metrorail station areas.

A number of the county's residential neighborhoods and larger garden-style apartment complexes are listed in the National Register of Historic Places and/or designated under the County government's zoning ordinance as local historic preservation districts. These include Arlington Village, Arlington Forest, Ashton Heights, Buckingham, Cherrydale, Claremont, Colonial Village, Fairlington, Lyon Park, Lyon Village, Maywood, Nauck, Penrose, Waverly Hills and Westover. Many of Arlington County's neighborhoods participate in the Arlington County government's Neighborhood Conservation Program (NCP). Each of these neighborhoods has a Neighborhood Conservation Plan that describes the neighborhood's characteristics, history and recommendations for capital improvement projects that the County government funds through the NCP.

Arlington is often spoken of as divided between North Arlington and South Arlington, which designate the sections of the county that lie north and south of Arlington Boulevard. Places in Arlington are often identified by their location in one or the other. Much consideration is given to socioeconomic and demographic differences between these two portions of the county and the respective amounts of attention they receive in the way of public services.

Arlington ranks fourth in the nation, immediately after Washington, D.C., for park access and quality in the 2018 ParkScore ranking of the top 100 park systems across the United States, according to the ranking methodologies of Trust for Public Land.

The climate in the county is characterized by hot, humid summers, mild to moderately cold winters, and pleasant spring and fall seasons. Arlington County averages 41.82 inches of precipitation that is fairly evenly spread out during the year. Snowfall averages 13.7 inches per year. The snowiest months are January and February, although snow also falls in December and March; scarce snow may fall in November or April. The county usually has 60 nights with lows below freezing and 40 days with highs in the 90s. Hundred degree temperatures readings are rare, even more so negative temperature readings in Fahrenheit, last occurring August 13, 2016, and January 19, 1994, respectively. According to the Köppen Climate Classification system, Arlington County has a slightly colder version of the humid subtropical climate, abbreviated "Cfa" on climate maps.

As of the 2010 census, there were 207,627 people, 98,050 households, and 41,607 families residing in Arlington. The population density was 8,853 people per square mile, the second highest of any county in Virginia.

According to the US Census, the racial makeup of the county in 2012 was 63.8% Non-Hispanic white, 8.9% Non-Hispanic Black or African American, 0.8% Non-Hispanic Native American, 9.9% Non-Hispanic Asian, 0.1% Pacific Islander, 0.29% Non-Hispanic other races, 3.0% Non-Hispanics reporting two or more races. 15.4% of the population was Hispanic or Latino of any race (3.4% Salvadoran, 2.0% Bolivian, 1.7% Mexican, 1.5% Guatemalan, 0.8% Puerto Rican, 0.7% Peruvian, 0.6% Colombian). 28% of Arlington residents were foreign-born as of 2000.

There were 86,352 households, out of which 19.30% had children under the age of 18 living with them, 35.30% were married couples living together, 7.00% had a female householder with no husband present, and 54.50% were non-families. 40.80% of all households were made up of individuals, and 7.30% had someone living alone who was 65 years of age or older. The average household size was 2.15 and the average family size was 2.96.

Families headed by single parents were the lowest in the DC area, under 6%, as estimated by the Census Bureau for the years 2006–2008. For the same years, the percentage of people estimated to be living alone was the third highest in the DC area, at 45%. In 2009, Arlington was highest in the Washington DC Metropolitan area for the percentage of people who were single – 70.9%. 14.3% were married. 14.8% had families. In 2014 Arlington had the 2nd highest concentration of roommates after San Francisco among the 50 largest U.S. cities.

According to a 2007 estimate, the median income for a household in the county was $94,876, and the median income for a family was $127,179. Males had a median income of $51,011 versus $41,552 for females. The per capita income for the county was $37,706. About 5.00% of families and 7.80% of the population were below the poverty line, including 9.10% of those under age 18 and 7.00% of those age 65 or over.

The age distribution was 16.50% under 18, 10.40% from 18 to 24, 42.40% from 25 to 44, 21.30% from 45 to 64, and 9.40% who were 65 or older. The median age was 34 years. For every 100 females, there were 101.50 males. For every 100 females age 18 and over, there were 100.70 males.

CNN Money ranked Arlington as the most educated city in 2006 with 35.7% of residents having held graduate degrees. Along with five other counties in Northern Virginia, Arlington ranked among the twenty American counties with the highest median household income in 2006. In 2009, the county was second in the nation (after nearby Loudoun County) for the percentage of people ages 25–34 earning over $100,000 annually (8.82% of the population). In September 2012, CNN Money ranked Arlington fourth in the country in its listing of "Best Places for the Rich and Single."

In 2008, 20.3% of the population did not have medical health insurance. In 2010, AIDS prevalence was 341.5 per 100,000 population. This was eight times the rate of nearby Loudoun County and one-quarter the rate of the District of Columbia.

Crime statistics for 2009 included the report of 2 homicides, 15 forcible rapes, 149 robberies, 145 incidents of or aggravated assault, 319 burglaries, 4,140 incidents of larceny, and 297 reports of vehicle theft. This was a reduction in all categories from the previous year.

According to a 2016 study by Bankrate.com, Arlington is the best place to retire, with nearby Alexandria coming in at second place. Criteria of the study included cost of living, rates of violent and property crimes, walkability, health care quality, state and local tax rates, weather, local culture and well-being for senior citizens.

2023 marked the sixth consecutive year that the American College of Sports Medicine named Arlington the "Fittest City in America" in their annual Fitness Index. Arlington topped the list of 100 cities in both the Personal and the Community & Environment Health metrics.

For the last two decades, Arlington has been a Democratic stronghold at nearly all levels of government. However, during a special election in April 2014, a Republican running as an independent, John Vihstadt, captured a County Board seat, defeating Democrat Alan Howze 57% to 41%; he became the first non-Democratic board member in fifteen years. This was in large part a voter response to plans to raise property taxes to fund several large projects, including a streetcar and an aquatics center. County Board Member Libby Garvey, in April 2014, resigned from the Arlington Democratic Committee after supporting Vihstadt's campaign over Howze. Eight months later, in November's general election, Vihstadt won a full term; winning by 56% to 44%. This is the first time since 1983 that a non-Democrat won a County Board general election. In 2018, without the controversial streetcar issue to bolster his campaign, Vihstadt lost.

The county is governed by a five-person County Board; members are elected at-large on staggered four-year terms. They appoint a county manager, who is the chief executive of the County Government. Like most Virginia counties, Arlington has five elected constitutional officers: a clerk of court, a commissioner of revenue, a commonwealth's attorney, a sheriff, and a treasurer. The budget for the fiscal year 2009 was $1.177 billion.

Under Virginia law, the only municipalities that may be contained within counties are incorporated towns; incorporated cities are independent of any county. Arlington, despite its population density and largely urban character, is wholly unincorporated with no towns inside its borders. In the 1920s, a group of citizens petitioned the state courts to incorporate the Clarendon neighborhood as a town, but this was rejected; the Supreme Court of Virginia held, in Bennett v. Garrett (1922), that Arlington constituted a "continuous, contiguous, and homogeneous community" that should not be subdivided through incorporation.

Current state law would prohibit the incorporation of any towns within the county because the county's population density exceeds 200 persons per square mile.[100] In 2017, then-county board chairman Jay Fisette suggested that the county as a whole should incorporate as an independent city.[101]

In 2009, Republican Attorney General Bob McDonnell won Virginia by a 59% to 41% margin, but Arlington voted 66% to 34% for Democratic State Senator Creigh Deeds.[102] The voter turnout was 42.78%.[103]

Arlington elects four members of the Virginia House of Delegates and two members of the Virginia State Senate. State Senators are elected for four-year terms, while Delegates are elected for two-year terms.

In the Virginia State Senate, Arlington is split between the 30th, 31st, and 32nd districts, represented by Adam Ebbin, Barbara Favola, and Janet Howell, respectively. In the Virginia House of Delegates, Arlington is divided between the 45th, 47th, 48th, and 49th districts, represented by Mark Levine, Patrick Hope, Rip Sullivan, and Alfonso Lopez, respectively. All are Democrats.

Arlington is part of Virginia's 8th congressional district, represented by Democrat Don Beyer.

The U.S. Postal Services designates Zip Codes starting with "222" for exclusive use in Arlington County. However, federal institutions, like Ronald Reagan Washington National Airport and The Pentagon use Washington, D.C. Zip Codes.

Arlington has consistently had the lowest unemployment rate of any jurisdiction in Virginia.[107] The unemployment rate in Arlington was 1.9% in July 2023.[108] 60% of office space in the Rosslyn-Ballston corridor is leased to government agencies and government contractors.[109] There were an estimated 205,300 jobs in the county in 2008. About 28.7% of these were with the federal, state or local government; 19.1% technical and professional; 28.9% accommodation, food and other services.[110]

In October 2008, BusinessWeek ranked Arlington as the safest city in which to weather a recession, with a 49.4% share of jobs in "strong industries".[111] In October 2009, during the Great Recession, the unemployment in the county reached 4.2%. This was the lowest in the state, which averaged 6.6% for the same time period, and among the lowest in the nation, which averaged 9.5% for the same time.[112]

In 2021, there were an estimated 119,447 housing units in the county.[113] In 2010, there were an estimated 90,842 residences in the county.[114] In March 2024, the median home cost $717,500 and the average cost $881,925.[115] 4,721 houses, about 10% of all stand-alone homes, were worth $1 million or more. By comparison, in 2000, the median single family home price was $262,400. About 123 homes were worth $1 million or more.[116]

In 2010, 0.9% of the homes were in foreclosure. This was the lowest rate in the DC area.[117]

14% of the nearly 150,000 people working in Arlington live in the county, while 86% commute in, with 27% commuting from Fairfax County. An additional 90,000 people commute out for work, with 42% commuting to DC, and 29% commuting to Fairfax County.[118]

A number of federal agencies are headquartered in Arlington, including the Air Force Office of Scientific Research, American Battle Monuments Commission, DARPA, Diplomatic Security Service, Drug Enforcement Administration, Foreign Service Institute, the DHS National Protection and Programs Directorate, Nuclear Waste Technical Review Board, Office of Naval Research, Transportation Security Administration, United States Department of Defense, United States Marshals Service, the United States Trade and Development Agency, and the U.S. AbilityOne Commission.

Companies headquartered in Arlington include Amazon (its second headquarters), AES, Axios, Alcalde and Fay, Arlington Asset Investment, AvalonBay Communities, Bloomberg Industry Group, CACI, Graham Holdings, Naviance, Rosetta Stone, Save America, and Nestlé USA. Boeing announced on May 5, 2022, that it would be moving its global headquarters to Arlington after more than 20 years in Chicago.[119] On June 7, 2022, RTX Corporation (formerly Raytheon) announced its global headquarters relocation to Arlington.[120] On February 13, 2024, CoStar Group announced the move of their global headquarters to Arlington after more than 10 years in DC.[121] Arlington is also the location of Washington, D.C. area regional offices for several consulting firms and is the global headquarters of many aerospace manufacturing and defense industry companies.

Organizations located here include the American Institute in Taiwan, Army Emergency Relief, The Conservation Fund, Conservation International, the Consumer Electronics Association, The Fellowship, the Feminist Majority Foundation, the Insurance Institute for Highway Safety, the National Rural Electric Cooperative Association, The Nature Conservancy, the Navy-Marine Corps Relief Society, the Public Broadcasting Service, United Service Organizations, and the US-Taiwan Business Council.

Arlington also has an annex of the South Korean embassy.[122]

Politico, a political focused digital based newspaper is based in Arlington.[123]

Axios, an American news website, founded by former Politico employees, focused on multiple subjects, in particular the collision between Technology and other subjects.[124][125]

According to the county's 2023 Comprehensive Annual Financial Report,[126] the top employers in the county are:

Arlington has been recognized as a strong incubator for start-up businesses, with a number of public/private incubators and resources dedicated to fostering entrepreneurship in the county.[127]

Arlington National Cemetery is an American military cemetery established during the American Civil War on the grounds of Confederate General Robert E. Lee's home, Arlington House (also known as the Custis-Lee Mansion). It is directly across the Potomac River from Washington, D.C., north of the Pentagon. With around 400,000 graves covering 639 acres, Arlington National Cemetery is the second-largest national cemetery in the United States.[128]

Arlington House was named after the Custis family's homestead on Virginia's Eastern Shore. It is associated with the families of Washington, Custis, and Lee. Begun in 1802 and completed in 1817, it was built by George Washington Parke Custis. After his father died, young Custis was raised by his grandmother and her second husband, the first US President George Washington, at Mount Vernon. Custis, a far-sighted agricultural pioneer, painter, playwright, and orator, was interested in perpetuating the memory and principles of George Washington. His house became a "treasury" of Washington heirlooms.[129]

In 1804, Custis married Mary Lee Fitzhugh. Their only child to survive infancy was Mary Anna Randolph Custis, born in 1808. Young Robert E. Lee, whose mother was a cousin of Mrs. Custis, frequently visited Arlington. Two years after graduating from West Point, Lieutenant Lee married Mary Custis at Arlington on June 30, 1831. For 30 years, Arlington House was home to the Lees. They spent much of their married life traveling between U.S. Army duty stations and Arlington, where six of their seven children were born. They shared this home with Mary's parents, the Custis family.[130]

When George Washington Parke Custis died in 1857, he left the Arlington estate to Mrs. Lee for her lifetime and afterward to the Lees' eldest son, George Washington Custis Lee.[131]

After the secession of Virginia towards the beginning of the Civil War, Mary Custis and Robert E. Lee left the estate permanently. Citing a failure to pay taxes, the U.S. government confiscated Arlington House and 200 acres (81 ha) of property from the Lees on January 11, 1864. On June 15, 1864, the U.S. government and Secretary of War Edwin M. Stanton designated the grounds as a military cemetery. In 1882, after many years in the lower courts, the matter of the ownership of Arlington House and its land was brought before the United States Supreme Court by George Washington Custis Lee. The Court decided that the property rightfully belonged to the Lee family. Shortly, the United States Congress appropriated the sum of $150,000 for the purchase of the property from the Lee family in March 1883.[131]

Veterans from all the nation's wars are buried in the cemetery, from the American Revolution through the military actions in Afghanistan and Iraq. Pre-Civil War dead were re-interred after 1900.[citation needed]

The Tomb of the Unknowns, also known as the Tomb of the Unknown Soldier, stands atop a hill overlooking Washington, DC. President John F. Kennedy is buried in Arlington National Cemetery with his wife Jacqueline Kennedy Onassis and some of their children. His grave is marked with an eternal flame. His brothers, Senators Robert F. Kennedy and Edward M. Kennedy, are also buried nearby. William Howard Taft, who was also a Chief Justice of the U.S. Supreme Court, is the only other President buried at Arlington.

Other frequently visited sites near the cemetery are the U.S. Marine Corps War Memorial, commonly known as the Iwo Jima Memorial, the U.S. Air Force Memorial, the Women in Military Service for America Memorial, the Netherlands Carillon and the U.S. Army's Fort Myer.[citation needed]

The Pentagon in Arlington is the headquarters of the United States Department of Defense. It was dedicated on January 15, 1943, and it is the world's second-largest office building. Although it is located in Arlington County, the United States Postal Service requires that "Washington, D.C." be used as the place name in mail addressed to the six ZIP codes assigned to The Pentagon.[132]

The building is pentagon-shaped and houses about 24,000 military and civilian employees and about 3,000 non-defense support personnel. It has five floors and each floor has five ring corridors. The Pentagon's principal law enforcement arm is the United States Pentagon Police, the agency that protects the Pentagon and various other DoD jurisdictions throughout the National Capital Region.[133]

Built during World War II, the Pentagon is the world's largest low-rise office building with 17.5 miles (28.2 km) of corridors, yet it takes only seven minutes to walk between its furthest two points.[134]

It was built from 689,000 short tons (625,000 t) of sand and gravel dredged from the nearby Potomac River[134] that were processed into 435,000 cubic yards (330,000 m3) of concrete and molded into the pentagon shape. Very little steel was used in its design due to the needs of the war effort.[135]

The open-air central plaza in the Pentagon is the world's largest "no-salute, no-cover" area (where U.S. servicemembers need not wear hats nor salute). Before being torn down in 2006, a hot dog stand occupied Ground Zero at the center of the courtyard. The food stand was reportedly a Soviet target during the Cold War due to the legend of a secret bunker entrance hidden beneath it.[136]

During World War II, the earliest portion of the Henry G. Shirley Memorial Highway was built in Arlington in conjunction with the parking and traffic plan for the Pentagon. This early freeway, opened in 1943 and completed to Woodbridge, in 1952, is now part of I-395.[citation needed]

The Pentagon Memorial, commemorating victims in the September 11 attacks, is located outside of the Pentagon and is a major tourist attraction.

Arlington forms part of the region's core transportation network. The county is traversed by two interstate highways: I-66 in the northern part of the county and I-395 in the eastern part, both with HOV lanes or restrictions. In addition, the county is served by the George Washington Memorial Parkway. In total, Arlington County maintains 376 miles (605 km) of roads.[137]

The street names in Arlington generally follow a unified countywide convention. The north–south streets are generally alphabetical, starting with one-syllable names, then two-, three- and four-syllable names. The first alphabetical street is Ball Street. The last is Arizona. Many east–west streets are numbered. Route 50 divides Arlington County. Streets are generally labeled North above Route 50, and South below.

Arlington has more than 100 miles (160 km) of on-street and paved off-road bicycle trails.[138] Off-road trails travel along the Potomac River or its tributaries, abandoned railroad beds, or major highways, including Four Mile Run Trail that travels the length of the county; the Custis Trail, which runs the width of the county from Rosslyn; the Washington & Old Dominion Railroad Trail (W&OD Trail) that travels 45 miles (72 km) from the Shirlington neighborhood out to western Loudoun County; and the Mount Vernon Trail that runs for 17 miles (27 km) along the Potomac, continuing through Alexandria to Mount Vernon.

Forty percent of Virginia's transit trips begin or end in Arlington, with the vast majority originating from Washington Metro rail stations.[139]

Arlington is served by the Washington Metropolitan Area Transit Authority (WMATA or Metro), the regional transit agency covering parts of Northern Virginia, Maryland, and Washington, D.C. Arlington has stations on the Blue, Orange, Silver and Yellow lines of the Washington Metro rail system. Arlington is also served by WMATA's regional Metrobus service. This includes Metroway, the first bus rapid transit (BRT) in the D.C. area, a joint project between WMATA, Arlington County, and Alexandria, with wait times similar to those of Metro trains. Metroway began service in August 2014.[140]

Arlington also operates its own county bus system, Arlington Transit (ART), which supplements Metrobus service with in-county routes and connections to the rail system.[141]

The Virginia Railway Express commuter rail system has one station in Arlington County, at the Crystal City station. Public bus services operated by other Northern Virginia jurisdictions include some stops in Arlington, most commonly at the Pentagon. These services include DASH (Alexandria Transit Company), Fairfax Connector, PRTC OmniRide (Potomac and Rappahannock Transportation Commission), and the Loudoun County Commuter Bus.[142][143]

Capital Bikeshare, a bicycle sharing system, began operations in September 2010 with 14 rental locations primarily around Washington Metro stations throughout the county.[144]

Arlington County is home to Ronald Reagan Washington National Airport, which provides domestic air services to the Washington, D.C., area. In 2009, Condé Nast Traveler readers voted it the country's best airport.[145] Nearby international airports are Washington Dulles International Airport, located in Fairfax and Loudoun counties in Virginia, and Baltimore-Washington International Thurgood Marshall Airport, located in Anne Arundel County, Maryland.

In 2007, the county authorized EnviroCAB, a new taxi company, to operate exclusively with a hybrid-electric fleet of 50 vehicles and also issued permits for existing companies to add 35 hybrid cabs to their fleets. As operations began in 2008, EnvironCab became the first all-hybrid taxicab fleet in the United States, and the company not only offset the emissions generated by its fleet of hybrids, but also the equivalent emissions of 100 non-hybrid taxis in service in the metropolitan area.[146][147] The green taxi expansion was part of a county campaign known as Fresh AIRE, or Arlington Initiative to Reduce Emissions, that aimed to cut production of greenhouse gases from county buildings and vehicles by 10 percent by 2012.[146] Arlington has a higher than average percentage of households without a car. In 2015, 13.4 percent of Arlington households lacked a car, and dropped slightly to 12.7 percent in 2016. The national average is 8.7 percent in 2016. Arlington averaged 1.40 cars per household in 2016, compared to a national average of 1.8.[148]

Arlington Public Schools operates the county's public K-12 education system of 22 elementary schools, six middle schools, Dorothy Hamm Middle School, Gunston Middle School, Kenmore Middle School, Swanson Middle School, Thomas Jefferson Middle School, and Williamsburg Middle School, and three public high schools, Wakefield High School, Washington-Liberty High School, and Yorktown High School. H-B Woodlawn and Arlington Tech are alternative public schools. Arlington County spends about half of its local revenues on education. For the FY2013 budget, 83 percent of funding was from local revenues, and 12 percent from the state. Per pupil expenditures are expected to average $18,700, well above its neighbors, Fairfax County ($13,600) and Montgomery County ($14,900).[150]

Arlington has an elected five-person school board whose members are elected to four-year terms. Virginia law does not permit political parties to place school board candidates on the ballot.[151]

Through an agreement with Fairfax County Public Schools approved by the school board in 1999, up to 26 students residing in Arlington per grade level may be enrolled at the Thomas Jefferson High School for Science and Technology in Fairfax at a cost to Arlington of approximately $8,000 per student. For the first time in 2006, more students (36) were offered admission in the selective high school than allowed by the previously established enrollment cap.[152]

The Roman Catholic Diocese of Arlington helps provide Catholic education in northern Virginia, with early learning centers, elementary and middle schools at the parish level. Bishop Denis J. O'Connell High School is the diocese's Catholic high school within Arlington County.

Marymount University is the only university with its main campus located in Arlington County. Founded in 1950 by the Religious of the Sacred Heart of Mary as Marymount College of Virginia, both its main campus and its Ballston Center are located on North Glebe Road, with a shuttle service connecting the two.

George Mason University operates an Arlington campus in the Virginia Square area between Clarendon and Ballston. The campus houses the Antonin Scalia Law School, the School of Policy, Government, and International Affairs, and the Jimmy and Rosalynn Carter School for Peace and Conflict Resolution.

In June 2011, Virginia Tech opened the Virginia Tech Research Center - Arlington in Ballston, providing a teaching and research base for graduate students in computer research and engineering to interact with organizations and research agencies in the National Capital area.[153]

Rosslyn is a location for some of the University of Virginia's business programs, including McIntire School of Commerce Master of Science in the Management of Information Technology, and Darden School of Business Master of Business Administration (Executive/Global Executive).

Other private and technical schools maintain a campus in Arlington, including the Institute for the Psychological Sciences, the John Leland Center for Theological Studies, the University of Management and Technology, DeVry University. Strayer University has a campus in Arlington as well as its corporate headquarters.

Anthem Education Group, George Washington University, Georgetown University, Northern Virginia Community College, Troy University, the University of New Haven, and the University of Oklahoma all have campuses in Arlington.

Arlington Sister City Association (ASCA) is a nonprofit organization affiliated with Arlington County, Virginia. ASCA works to enhance and promote the region's international profile and foster productive exchanges in education, commerce, culture and the arts through a series of activities. Established in 1993, ASCA supports and coordinates the activities of Arlington County's five sister cities:[154]

Notable individuals who reside or who have resided in Arlington County include: