United States Custom House and Post Office (Third and Olive)

A four-story classical federal building of stone over a rusticated base. Its principal front on Third Street was carried on six Corinthian columns, and the design made pioneering use of cast iron under the Treasury's specifications. Along the flank a bracketed modillion cornice ran beneath the roof, a second cornice divided the upper floors, the third-story windows wore triangular pediments, and round-arched second-story windows sat above a belt course between quoined corners.

Congress appropriated funds in 1850 for a federal building in St. Louis, and George I. Barnett was named supervising architect in 1852; construction ran from 1854 to 1859. Reputed the largest federal building west of the Mississippi when new, it housed the Post Office, the Custom House, and the federal courts — the setting for the Whiskey Ring trials of the 1870s. After Alfred B. Mullett's much larger Custom House and Post Office opened farther west on Olive Street in 1884, the old building was given over to warehouse use. It was demolished around 1939–1941 in the riverfront clearance that created the Jefferson National Expansion Memorial — the Gateway Arch grounds.