Fairfax County is a county in Virginia, in the United States. As of the 2010 census, the population of the county is 1,081,726, making it the most populous jurisdiction in the Commonwealth of Virginia, with 13.5% of Virginia's population. The county is also the most populous jurisdiction in the Washington Metropolitan Area, with 19.8% of the MSA population, as well as the larger Baltimore–Washington Metropolitan Area, with 13.1% of the CSA population.
Fairfax was the first county in the United States to reach a six-figure median household income, and has the second-highest median household income of any local jurisdiction in the United States after neighbor Loudoun County.
The county is home to the headquarters of intelligence agencies such as the Central Intelligence Agency, National Geospatial-Intelligence Agency, and National Reconnaissance Office, as well as the National Counterterrorism Center and Office of the Director of National Intelligence. The county is also home to ten of the metropolitan area's Fortune 500 companies.
At the time of European encounter, the inhabitants of the area that became Fairfax County were a Algonquian-speaking sub-group of the Powhatan tribal confederation called the Tauxenent. They inhabited a village called Namassingakent on the south bank of the Potomac River in what is now Fairfax County.
The oldest settlements in Fairfax County were located along the Potomac River. George Washington settled in Fairfax County and built his home, Mount Vernon, facing the river. Gunston Hall, the home of George Mason is located nearby. Modern Fort Belvoir is partly located on the estate of Belvoir Manor, built along the Potomac by William Fairfax in 1741. Thomas Fairfax, 6th Lord Fairfax of Cameron, the only member of the British nobility ever to reside in the colonies, lived at Belvoir before he moved 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 gradually 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 of the District of Columbia. 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. The Fairfax County town of Falls Church became an independent city in 1948. The Fairfax County town of Fairfax became an independent city in 1961.
Located near Washington, D.C., Fairfax County was an important region in the Civil War. The Battle of Chantilly or Ox Hill, during the same campaign as the second Battle of Bull Run, was fought within the county; Bull Run is the border between Fairfax and Prince William County. Other areas of activity included Minor's Hill, Munson's Hill, and Upton's Hill, on the eastern border of the county, overlooking Washington, D.C.
The growth of the federal government in the years during and after World War II spurred rapid growth in the county. As a result, the once rural county began to become increasingly suburban. Other large businesses continued to settle in Fairfax County and the opening of Tysons Corner Center spurred the rise of Tysons Corner itself. The technology boom and a steady government-driven economy also created rapid growth and an increasingly growing and diverse population. The economy has also made Fairfax County one of the wealthiest counties in the nation.
Note: 1960 corrected population 262,482 (including Falls Church city, 272,674). See also notes C1, C12, and C13.