Mather Gorge is the Potomac River’s steep, cliff-lined passage just below Great Falls along the Maryland-Virginia border, named for National Park Service director Stephen Mather. Bear Island and Chesapeake and Ohio Canal National Historical Park edge the Maryland side, while Great Falls Park borders the Virginia side. Here the river forms one of the Potomac’s most dramatic stretches near Washington before opening southward into the broader Potomac Gorge and crossing the Fall Line at Little Falls. Long associated with recreation, the gorge is known for the Billy Goat Trail, the River Trail, notable top-rope climbing cliffs, and whitewater rapids from Class I to Class VI.