when was the national mall in washington dc built
National Mall The Washington City Canal, completed in 1815 in accordance with the L'Enfant Plan, travelled along the former course of Tiber Creek to the Potomac River along the present line of Constitution Avenue, NW (formerly B Street, NW) and south around the Capitol, thus defining the northern and eastern boundaries of the Mall.[15][16][17] Being shallow and often obstructed by silt, the canal served only a limited role and became an open sewer.[15] The portion of the canal that traveled near the Mall was covered over in 1871 for sanitary reasons.[15]