Park · Washington DC
Leashed dogs (6ft) on all trails and open ground — the leash must be held, not merely attached. Not all areas permit dogs; the signs say which.
Seventeen hundred acres of wooded valley running right up the middle of the city, with thirty-two miles of trail in it.
The policy above is the standing rule of the agency that manages this land, as published on its own pages. Official page.
Rules change, and seasonal beach rules change twice a year. Check before a long drive.