Cross Section of Proposed Addition to SIB, by Meigs, Montgomery C (Montgomery Cunningham) 1816-1892, 1877, Smithsonian Archives - History Div, Rendering by General Montgomery Meigs of a longitudinal section (south to north) of a proposed addition to Smithsonian Institution Building adjoining the old south tower. This addition would contain the new National Museum Building that would be attached to the Smithsonian Institution Building on the south side. This addition was never built; a separate building, now known as the Arts and Industries Building, was built to the east of the Castle and opened in 1881..