Fairfax County, officially the County of Fairfax, is a county in the U.S. state of Virginia. As of the 2010 census, the population was 1,081,726, in 2013, the population was estimated to be 1,116,897, making it the most populous jurisdiction in the Commonwealth of Virginia, with 13.6% of Virginia’s population. The county is also the most populous jurisdiction in the Washington Metropolitan Area, with 19.8% of the MSA population. The county seat is Fairfax. 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 Fortune 500 companies, including three with Falls Church addresses. 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. 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 Counties. The growth of the federal government in the years during and after World War II spurred rapid growth in the county. 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. Like the rest of the Washington, D.C. metropolitan area, the county experiences a climate of hot, humid summers and cool winters, with occasional heavy snowfalls during nor’easters. Spring and early autumn are the periods with most pleasant weather. Tropical cyclones affect the county only infrequently because of its inland location and northerly latitude.