Leesburg is a historic town within and the county seat of Loudoun County, Virginia. Leesburg is located 33 miles (53km) west-northwest of Washington, D.C. along the base of Catoctin Mountain and adjacent to the Potomac River. Its population according 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. Leesburg, like the rest of Loudoun, has undergone considerable growth and development over the last 30 years, transforming from a small, rural, piedmont town to a suburbanbedroom community for commuters to the national capital. Current growth in the town and its immediate area to the east (Lansdowne/Ashburn) concentrates along the Dulles Greenway and State Route 7, which roughly parallels the Potomac River between Winchester to the west and Alexandria to the east. The Federal Aviation Administration's Washington Air Route Traffic Control Center is located in Leesburg.