The Potomac River flows into the Chesapeake Bay, and is approximately 413 miles long. It runs along the western border of Maryland, past Washington, D.C., Fort Washington Park and separates eastern Virginia from western Maryland.

The source of the North Branch Potomac River is Fairfax Stone located at the intersection of Maryland and West Virginia. The source of the South Branch Potomac River begins near Green Spring in West Virginia.

The headwaters of the Potomac River flow through the Potomac State Forest, which occupies 12,000 acres of forest. The forest's highest point, Backbone Mountain (3,220 feet) offers views of the river and forests below.

About fifteen miles northwest of Washington, D.C. is the Great Falls of the Potomac. At the edge of the Piedmont Plateau, where the fall line begins, water builds speed and pours down the steep rocks that comprise the falls, flowing through Mather Gorge. At Great Falls Park, there are three overlooks showcasing the various vantage points of the falls. Hiking trails, including the River Trail and the Patowmack Canal Trail, are available as well as picnic sites and ranger led activities.