Great Falls of the Potomac River

Great Falls
View of the Great Falls from Virginia
Location	Montgomery County, Maryland and Fairfax County, Virginia
Type	Cascade
Total height	76 ft
Watercourse	Potomac River

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.

Scenic views are offered on both the Maryland side and the Virginia side. The Billy Goat Trail on Bear Island, accessible from Maryland, offers scenic views of the Great Falls, as do vantage points on Olmsted Island (also accessible from Maryland). There are overlook points on the Virginia side.

The Great Falls area is popular for outdoor activities such as kayaking, whitewater rafting, rock climbing, and hiking.

Great Falls and Little Falls (about 5 miles downstream) are named in contradistinction to one another.

Roughly 35,000 years ago, the Potomac River began carving out the Great Falls of the Potomac. The river cascades over a series of 20-foot (6.1 m) falls, falling a total of 76 feet (23 m) in elevation over a distance of less than 1 mile (1.6 km).

The Potomac narrows significantly as it passes over the falls and through Mather Gorge. Heavy rain or snow in the watershed upstream causes white-water floods which entirely submerge the rocks and even threaten the adjacent park visitor center (built on stilts for this reason). A pillar at the Virginia overlook, well above the river, marks the level of the 1936 Potomac Flood.