Leesburg is a historic town in, and county seat of, Loudoun County, Virginia, United States of America. Leesburg is located approximately 40 miles (64 km) west-northwest of Washington, D.C. along the base of the Catoctin Mountain and adjacent to the Potomac River. The town is also the northwestern terminus of the Dulles Greenway (a private toll road which 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 suburban bedroom community for commuters to the national capital. Current growth in the town and its immediate area to the east 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.