Loudoun County is a county in the Commonwealth of Virginia in the United States. In 2015, the population was estimated at 375,629, making it Virginia’s third-most populous county. Loudoun County’s seat is Leesburg. Loudoun County is part of the Washington–Arlington–Alexandria, DC–VA–MD–WV Metropolitan Statistical Area.
As of 2012, Loudoun County had a median household income of $117,876. Since 2008, the county has been ranked first in the U.S. in median household income among jurisdictions with a population of 65,000 or more.