Loudoun County, Virginia

Loudoun County
Loudoun County Courthouse and a World War II monument (right) in Leesburg, February 2021
Motto: 
"I Byde My Time"
Location within the U.S. state of Virginia
Virginia's location within the U.S.
Coordinates: 39°05′N 77°38′W / 39.09°N 77.64°W / 39.09; -77.64
Country United States
State Virginia
Founded1757
Named afterJohn Campbell, 4th Earl of Loudoun
SeatLeesburg
Largest townLeesburg
Area
  Total
521.33 sq mi (1,350.2 km2)
  Land515.74 sq mi (1,335.8 km2)
  Water5.6 sq mi (15 km2)  1.1%
Population
 (2020)
  Total
420,959
  Density810/sq mi (310/km2)
Time zoneUTC−5 (Eastern)
  Summer (DST)UTC−4 (EDT)
Congressional district10th
Websiteloudoun.gov

Loudoun County (/ˈldən/) is in the northern part of the Commonwealth of Virginia in the United States. In 2020, the census returned a population of 420,959, making it Virginia's third-most populous county. The county seat is Leesburg. Loudoun County is part of the Washington–Arlington–Alexandria, DC–VA–MD–WV Metropolitan Statistical Area.

As of 2023, Loudoun County had a median household income of $156,821, the highest of any county or county equivalent in the nation.