This 384-foot-wide by 120-foot-high geodesic dome, located 20 miles north of St. Louis, was constructed as a repair and maintenance structure for railroad oil tank cars. Built in 1961 for the Union Tank Car Company by Synergetics, Inc., a company founded by architect and inventor R. Buckminster Fuller, it is a replica of an earlier tank car dome in Baton Rouge, Louisiana (1958; demolished 2008). At the time, the two domes were the world’s largest clear-span structures.

The Union Tank Car Dome’s steel skin walls are supported by an external web of 4-inch steel tubes and tension rods, arranged in hexagonal shapes and anchored to 80 concrete pilings. The tubes are attached at the center points of 321 separate 6-sided, quarter-inch-thick steel panels. The 2.5-acre interior is centered on an office and parts tower and circular transfer table, designed to switch the tank cars from inbound tracks to one of 30 repair tracks.

The dome concept represented a radical departure from the traditional linear covered railroad track maintenance facility. Battey and Childs, a Chicago architectural and engineering firm, supervised dome construction. The internal operations were designed by Dick Lehr of the Chicago-based Union Tank Car Company, a subsidiary of Standard Oil Company.

The dome is now occupied Watco Mechanical Services, a railroad car repair company.