Loudoun County, Virginia

Loudoun County ( ) is a county in the Commonwealth of Virginia. It is part of the Washington Metropolitan Area. The 2010 U.S. Census said 312,311 people live there. The number of people grew 84 percent over the 2000 census of 169,599. Its county seat is Leesburg.
As of 2007, Loudoun County has the highest median household income of any county in the United States ($107,207). This is higher than nearby Fairfax County, Virginia ($105,241).