Interactive Maps

The Lower Potomac

The Potomac Estuary

Mount Vernon to Anacostia River

Mall Area

Georgetown to Great Falls

Potomac Piedmont

Upper Potomac

The North Branch

Boat Ramps

Monitoring Sites

Bridges and Ferries

Cruises and Charters

Search Potomac Sites

Also Explore

St. Marys River

Maryland Tributary

This historic river flows 22.3 miles through southern St. Mary's County, Maryland. The river is 2 miles wide at its mouth and was an attractive spot for early settlers in Maryland. The colonial settlement became the first capital of Maryland and now features a large state historic area. The upper part of the river is the site of St. Mary's River State Park, which includes a 250-acre lake.

Suggested Links

Contact Information
Maryland Department of Natural Resources

MD

Website