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 Virginia’s most populous county. It was also rich in agriculture, and the county’s contributions of grain to George Washington’s Continental Army, earned it the nickname “Breadbasket of the Revolution.”
During the War of 1812, important Federal documents and government archives were evacuated from Washington and stored at Leesburg. Local tradition holds that these documents were stored at Rokeby House, making Leesburg briefly the capital of the United States.
U.S. President James Monroe treated Oak Hill Plantation as a primary residence from 1823 until his death on July 4, 1831. The Loudoun County coat of arms and flag, granted by the English College of Arms, memorialize the special relationship between Britain and the United States that developed through his Monroe Doctrine.
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.
In 1962, Washington Dulles International Airport was built in southeastern Loudoun County in Sterling. Since then, Loudoun County has experienced a high-tech boom and rapid growth. Accordingly, many have moved to eastern Loudoun and become residents of planned communities such as Sterling Park, Sugarland Run, Cascades, and Ashburn Farm, making that section a veritable part of the Washington suburbs. Others have moved to the county seat or to the small towns and rural communities of the Loudoun Valley.