Smithsonian Institution Building and The Mall, 1855, by Unknown, c. 1855, Smithsonian Archives - History Div, The Smithsonian Institution Building (SIB) seen from downtown Washington, D.C., from across The Mall, around 1855. In the foreground are construction materials along 15th Street, NW for the new wing added in 1855 to the Treasury Building. The Treasury building is the oldest departmental building in Washington, D.C.having been completed in 1842 and expanded three times by 1869. Residential and commercial buildings in the foreground are between 15th and 14th Streets, NW. This area was also known in the 1860s as the red light district called Murder Bay. The canal bordering the Mall before being converted to form Constitution Avenue is the sliver at right center. The white residence at the far left is at the corner of 15th Street and Pennsylvania Avenue, NW..