Great Falls is a series of rapids and waterfalls on the Potomac River, 14 miles (23 km) upstream from Washington, D.C., on the border of Montgomery County, Maryland and Fairfax County, Virginia. Great Falls Park, operated by the National Park Service, is located on the southern banks in Virginia, while Chesapeake and Ohio Canal parkland is located along the northern banks of the river in Maryland. The Potomac and the falls themselves are legally entirely within Maryland, with the state and county boundaries following the south bank of the river.