Denver's first train station was constructed in 1868 to serve the new Denver Pacific Railway, which connected Denver to the main transcontinental line at Cheyenne, Wyoming. By 1875, there were four different railroad stations, making passenger transfers between different railroad lines inconvenient. To remedy this issue, the Union Pacific Railroad proposed creating one central "Union Station" to combine the various operations. In February 1880, the owners of the four lines (the Union Pacific, the Denver & Rio Grande Western, the Denver, South Park & Pacific, and the Colorado Central) agreed to build a station at 17th and Wynkoop Streets. Architect A. Taylor of Kansas City was hired to develop the plans, and the station opened in May 1881.
A fire in 1894 destroyed the central portion of the 1881 depot. The Kansas City architectural firm of Van Brunt & Howe was hired to design a larger replacement depot in the Romanesque style. Both the 1881 and 1894 depots included a tall central clock tower with four clock faces.
In 1912, the original Union Depot partnership was dissolved and replaced by the Denver Terminal Railway Company, representing the then-major operators of the station (the Atchison, Topeka, & Santa Fe, the Chicago, Burlington, & Quincy, the Chicago, Rock Island, & Pacific, the Colorado & Southern, the Union Pacific, and the Denver & Rio Grande Westen). The new partnership decided to demolish and rebuild the central portion of the station to handle the increasing passenger traffic. The new central portion, designed by Denver architects Gove & Walsh, was built in the Beaux-Arts style and opened in 1914.