Fairfax County, officially the County of Fairfax, is a county in the state of Virginia, United States. With a population of 1,150,309 as of the 2020 census, it is the most populous county in Virginia, the most populous jurisdiction in the Washington metropolitan area, and the most populous location in the Washington–Baltimore combined statistical area. The county seat is Fairfax; however, because it is an independent city under Virginia law, the city of Fairfax is not part of the county.
The county is part of the Northern Virginia region and forms part of the suburban ring of Washington, D.C., the nation's capital. The county is predominantly suburban with some urban and rural pockets. It borders Montgomery County, Maryland to its north, Falls Church, Alexandria, Arlington County, and Prince George's County, Maryland to its east, Charles County, Maryland to its southeast, Prince William County to its southwest, and Loudoun County to its northwest.
The county is home to the offices of the director of national intelligence in McLean and the headquarters of four U.S. intelligence agencies: the Central Intelligence Agency at the George Bush Center for Intelligence in Langley, the National Geospatial-Intelligence Agency at Fort Belvoir, the National Reconnaissance Office in Chantilly, and the National Counterterrorism Center in McLean.
In academia, the county is home to the flagship campus of George Mason University in Fairfax, CIA University in Chantilly, Sherman Kent School for Intelligence Analysis in Reston, and several Northern Virginia Community College campuses. In the private sector, as of 2025, eleven of the Fortune 500 companies are headquartered in the county as of 2023.
In 2020, Fairfax County's median household income of $127,866 was the fifth-highest in the United States.
History
Prior to European settlement, present-day Fairfax County was initially inhabited by the Algonquian-speaking Doeg tribe.
17th century In 1608, Captain John Smith documented the Doeg tribe's villages, which included Namassingakent and Nemaroughquand on the south bank of the Potomac River in present-day Fairfax County. By 1670, Virginian colonists from the Northern Neck region drove the Doeg Tribe out of present-day Fairfax County and into Maryland.
18th century Fairfax County was formed in 1742 from the northern part of Prince William County, and was named after Thomas Fairfax, 6th Lord Fairfax of Cameron, proprietor of the Northern Neck. The county's logo, seal and flag were adopted from the arms of Lord Fairfax of Cameron.
The county's initial settlements were along the Potomac River. George Washington settled in Fairfax County and built his home, Mount Vernon, facing the Potomac. Gunston Hall, the home of George Mason, is nearby. Fort Belvoir is partly on the estate of Belvoir Manor, built along the Potomac by William Fairfax in 1741.
Thomas Fairfax, the only member of the British nobility ever to reside in the colonies, lived at Belvoir before moving to the Shenandoah Valley. The Belvoir mansion and several of its outbuildings were destroyed by fire immediately after the Revolutionary War in 1783, and George Washington noted the plantation complex deteriorated into ruins.
In 1757, the northwestern two-thirds of Fairfax County became Loudoun County. In 1789, part of Fairfax County was ceded to the federal government to form Alexandria County, then part of the District of Columbia.
19th century Alexandria County was returned to Virginia in 1846, reduced in size by the secession of the independent city of Alexandria in 1870, and renamed Arlington County in 1920.
During the American Civil War the Battle of Chantilly, also known as Ox Hill, part of the Second Battle of Bull Run, was fought within Fairfax County. Other areas of Civil War conflict in the county included Minor's Hill, Munson's Hill, and Upton's Hill.
20th century The Fairfax County town of Falls Church became an independent city in 1948.About Falls Church Retrieved June 10, 2009 The Fairfax County town of Fairfax was named an independent city in 1961.
The federal government's growth during and after World War II spurred rapid growth in the county and transformed it from a rural to suburban region. Large businesses began settling in the county, and the opening of Tysons Corner Center spurred the rise of Tysons, Virginia. The technology boom and a steady government-driven economy created rapid growth and an increasingly large and diverse population. The economy has also made Fairfax County one of the nation's wealthiest counties.
A general aviation airport along U.S. Route 50 west of Seven Corners, Falls Church Airpark, operated in the county from 1948 to 1960. The facility's 2,650-foot unpaved runway was used extensively by private pilots and civil defense officials. Residential development, multiple accidents, and the demand for retail space led to its closure in 1960.Freeman, Paul "Falls Church Airpark, Falls Church, VA" Abandoned & Little-Known Airfields. Retrieved March 19, 2014 Rollo, Vera (2003) Virginia Airports: A Historical Survey of Airports and Aviation From the Earliest Days. Richmond, VA: Virginia Aviation Historical Society Day, Kathleen (September 21, 1987) "Small Airports Nosediving in Number" The Washington Post, page B1
Geography and climate
According to the U.S. Census Bureau, the county has an area of , of which is land and (3.8%) is water. There are about 44,400,000 trees that create a canopy covering 55.4% of the total land area.
Fairfax County is bounded on the north and southeast by the Potomac River. Across the river to the northeast is Washington, D.C., across the river to the north is Montgomery County, Maryland, and across the river to the southeast are Prince George's County, Maryland and Charles County, Maryland. The county is partially bounded on the north and east by Arlington County and the independent cities of Alexandria and Falls Church. It is bounded on the west by Loudoun County, and on the south by Prince William County.
Most of the county lies in the Piedmont region, with rolling hills and deep stream valleys, such as Difficult Run and its tributaries. West of Route 28, the hills give way to a flat, gentle valley that stretches west to the Bull Run Mountains in Loudoun County. Elevations in the county range from near sea level along the tidal sections of the Potomac River in the southeast portion of the county to more than in the Tysons area.
In 2023, the plant hardiness zone shifted from 7a to 7b. The Fairfax County News Letter predicts that Fairfax will shift to zone 8 in the next few decades as temperatures rise.
Adjacent jurisdictions
Geology The Piedmont hills in the central county are made up of ancient metamorphic rocks such as schist, the roots of several ancestral ranges of the Appalachian Mountains. The western valley is floored with more recent shale and sandstone. This geology is similar to adjacent bands of rocks in Maryland and further south in Virginia along the eastern front of the Appalachian.
An area of of the county is known to be underlain with natural asbestos. Much of the asbestos is known to emanate from fibrous tremolite or actinolite. The threat was discovered in 1987, prompting the county to establish laws to monitor air quality at construction sites, control soil taken from affected areas, and require freshly developed sites to lay of clean, stable material over the ground.
During the construction of Centreville High School, for instance, a large amount of asbestos-laden soil was removed and then trucked to Vienna for the construction of the I-66/Nutley Street interchange. Fill dirt then had to be trucked in to make the site level. Marine clays can be found in widespread areas of the county east of Interstate 95, mostly in the Franconia and Mount Vernon districts. These clays contribute to soil instability, leading to significant construction challenges for builders.
Demographics Racial and ethnic composition +Fairfax County, Virginia – Racial and ethnic compositionRace / Ethnicity (NH = Non-Hispanic)Pop 1980Pop 1990Pop 2000Pop 2010 Pop 2020% 1980% 1990% 2000% 2010% 2020White alone (NH)514,330633,935624,296590,622542,00186.17%77.44%64.38%54.60%47.12%Black or African American alone (NH)34,61861,96481,28796,078108,3395.80%7.57%8.38%8.88%9.42%Native American or Alaska Native alone (NH)1,2351,8381,8341,8431,4370.21%0.22%0.19%0.17%0.12%Asian alone (NH)22,72568,140125,585188,737233,8583.81%8.32%12.95%17.45%20.33%Native Hawaiian or Pacific Islander alone (NH)x included in the Asian category in the 1980 Censusx included in the Asian category in the 1990 Census616779772xx0.06%0.07%0.07%Other race alone (NH)4,4588332,4733,3597,0460.75%0.10%0.26%0.31%0.61%Mixed race or Multiracial (NH)x not an option in the 1980 Censusx not an option in the 1990 Census26,70031,82657,622xx2.75%2.94%5.01%Hispanic or Latino (any race)19,53551,874106,958168,482199,2343.27%6.34%11.03%15.58%17.32%Total596,901818,584969,7491,081,7261,150,309 100.00%100.00%100.00%100.00%100.00%
Racial / Ethnic Profile of places in Fairfax County, Virginia (2020 Census)Following is a table of cities, villages, and census designated places in Fairfax County, Virginia. Data for the United States (with and without Puerto Rico), the state of Virginia, and Fairfax County itself have been included for comparison purposes. The majority racial/ethnic group is coded per the key below. Communities that extend into and adjacent county or counties are delineated with a followed by an accompanying explanatory note. The full population of each community has been tabulated including the population in adjacent counties. Majority minority with no dominant groupMajority WhiteMajority BlackMajority HispanicMajority Asian