Leesburg is a historic town within and the county seat of Loudoun County, Virginia. Leesburg is located west-northwest of Washington, D.C. along the base of Catoctin Mountain and adjacent to the Potomac River. Its population according to the 2010 Census is 42,616. The town is also the northwestern terminus of the Dulles Greenway, a private toll road that connects to the Dulles Toll Road at Washington Dulles International Airport.