D.C. Code § 10-139

All public spaces resulting from the filling of canals in the original City of Washington, except such portions as are included in the navy yard or in actual use as roadways and sidewalks, and except the portions assigned by law to the District of Columbia for use as a property yard and the location of a sewerage pumping station, respectively, are placed under the jurisdiction of the Director of the National Park Service and shall be laid out as reservations as a part of the park system of the District of Columbia.