Clarksville is a town founded in Mecklenburg County in the U.S. state of Virginia, near the southern border of the state. The population was 1,139 at the 2010 census. Since the town has numerous buildings of the 18th-, 19th-, and early 20th-century architecture, the downtown area of Clarksville has been designated an Historic District on the National Register of Historic Places and Virginia's Historic Register. Clarksville claims the title of Virginia's only Lakeside town.