Can't remember the name,but it goes over to the Pentagon. WABA(.org) has a list of all the local trails on their site.

There are two Key Bridge crossings in G'town;if you're on the west side of the bridge,there's a crosswalk that will put you on the sidewalk,if you're on the east side of the bridge you can get off the sidewalk at the light and head east on M street. Also on the east side of the bridge is Francis Scott Key park;if you cut through there it will take you down to the C&O Canal or you can cross the bridge over the canal and go down some steps to get under the Whitehurst. Turn right under there and you'll get on the Cap Crescent trail,turn left and you'll go past the waterfront which has a trail that runs past the Kennedy Center down to the Mall.