TJ Models released two "circus car" kits in the 1980s (this flat car and a 70' stock car). Each kit is a one-piece plastic casting (trucks and couplers not included). As pictured above, TJ also sold an assortment of plastic circus wagons (12' Cage Wagon, 16' Cage Wagon, 19' Baggage Wagon, 18' Ticket/Lunch Wagon).
Railroads charged by the number of cars moved, not the load, so circus owners purchased these longer flat cars, capable of carrying several wagons. The Mount Vernon was one of the most commonly used cars, serving any number of circus and carnival operations. The first circus flats of steel construction were sixty-foot cars. The first show to use these flats was the Buffalo Bill's Wild West show in 1911. By the 1920's the Warren Tank Car Company of Warren, Pennsylvania, and the Mt. Vernon Car Manufacturing Company of Mt. Vernon, Illinois, were the principle providers of the steel circus flat cars. In 1926, both these companies were competing heavily to get circuses to convert from the 60 foot cars to their new 70 and 72 foot flats.