Potomac River in e USA. It rises in West Virginia at the confluence of the North and South Branch rivers, and flows e and se to Chesapeake Bay on the Atlantic coast, forming the boundaries of Maryland-West Virginia and Maryland-Virginia. The river is navigable for large ships as far as Washington, D.C. Length: 462km (287mi).

Potomac a river of the eastern US, which rises in the Appalachian Mountains and flows through Washington DC into Chesapeake Bay. The report ‘All quiet along the Potomac’ is attributed to the Union general George B. McClellan (1826–85) at the time of the Civil War, although the words are also found in ‘The Picket Guard’ (1861), a poem by Ethel Lynn Beers (1827–79).