Loudoun County is a county located in the United States Commonwealth of Virginia, and is part of the Washington Metropolitan Area. As of the 2010 U.S. Census, the county is estimated to be home to 312,311 people, an 84 percent increase over the 2000 figure of 169,599. That increase makes the county the fourth fastest-growing in the United States during that period. Its county seat is Leesburg. As of 2007, the town had been county seat for 249 of the last 250 years.
As of 2007, Loudoun County has the highest median household income of any county in the United States ($107,207), beating neighboring Fairfax County, Virginia ($105,241). The two counties have been trading places as the highest-income county in the United States in recent years.
Loudoun County was established in 1757 from Fairfax County. The county is named for John Campbell, Fourth Earl of Loudoun and Governor General of Virginia from 1756–59. Western settlement began in the 1720s and 1730s with Quakers, Scots-Irish, Germans and others moving south from Pennsylvania and Maryland and by English and African slaves moving upriver from Tidewater.
By the time of the American Revolution, it was the most populous county in Virginia. During the War of 1812, important Federal documents and government archives were evacuated from Washington and stored at Leesburg for safe keeping. Local tradition holds that these documents were stored at Rokeby House and thus that Leesburg was briefly the capital of the United States.
Early in the American Civil War, the Battle of Balls Bluff took place near Leesburg on October 21, 1861. Future jurist Oliver Wendell Holmes, Jr. was critically wounded in that battle along the Potomac River. During the Gettysburg Campaign in June 1863, Confederate Major General J.E.B. Stuart and Union cavalry clashed in the battles of Aldie, Middleburg, and Upperville. Confederate partisan John S. Mosby based his operations in Loudoun and adjoining Fauquier County (for a more in-depth account of the history of Loudoun County during the Civil War, see Loudoun County in the American Civil War).
James Monroe constructed and resided at Oak Hill near Aldie after his presidency. American Civil War Brigadier General Robert H. Chilton (Chief of Staff under Robert E. Lee) was a native of Loudoun County. World War II general George C. Marshall resided at Dodona Manor in Leesburg. Essayist and journalist Russell Baker grew up in Morrisonville, Virginia and his book Growing Up highlights his childhood in rural Virginia. Entertainer Arthur Godfrey lived near historic Waterford, Virginia. Loudoun County is also notable for being the birthplace of Julia Neale Jackson, mother of Stonewall Jackson, and Susan Catherine Koerner, mother of the Wright Brothers.