During its heyday as a passenger rail facility, Union Terminal had a capacity of 216 trains per day, 108 in and 108 out. Three concentric lanes of traffic were included in the design of the building, underneath the main rotunda of the building: one for taxis, one for buses, and one (although never used) for streetcars. However, the time period in which the terminal was built was one of decline for train travel. By 1939, local newspapers were already describing the station as a white elephant.
While it had a brief revival in the 1940s, because of World War II, it declined in use through the 1950s and the 1960s. In July 1958, Union Terminal was witness to the end of an era as the last mainline passenger steam train in the United States, the Norfolk and Western #603, originated in Cincinnati.