Union Station is generally attributed to Theodore C. Link, as the predominate architect throughout the building project. He was joined by other architects in the initial phases, from 1891 -1894 when the station opened, and in the subsequent construction of the adjoining Terminal Hotel. Drawings early in the process were signed “Theo. C. Link and Edward A. Cameron.” Later tracings for the Terminal Hotel include work by Alfred Paist Rosenheim and William B. Ittner, along with Link.

St. Louis Union Station is considered by many experts to be the grandest and the most important railway edifice erected before the close of the 19th-century.  Combined with James Eads' successful endeavor to span the Mississippi River with a novel multi-level railway and pedestrian bridge that unimpeded river traffic, St. Louis Union Station stood as convincing proof that St. Louis was at the country's center for transportation in the middle-west.

The architects, Theodore C. Link and Edward A. Cameron, sought to purposely capture both the solidity and permanence of established European architectural styles coupled with clever and practical solutions to serve the [then] modern and thriving world of tractive steam locomotive engines.

The St. Louis Union Station train shed was designed by Washington University graduate George H. Pegram. Due to the enormous span planned for the St. Louis Union Station train shed, Pegram's patented railroad bridge truss design proved to be the most practical to fabricate. This resulted in the world's largest train shed, measuring 700 by 606 feet and supporting the operation of thirty-two terminating tracks and gates, nineteen miles of track line, 130 switches, and 103 signals.

A building of mammoth proportions and elegant ornamental decoration, St. Louis Union Station was intended to accommodate thousands of travelers and workers daily. The monumental head house featured numerous amenities including a luxurious hotel, a saloon, a dining hall, lunch rooms, lounges, ticket offices, several offices for the Terminal Railroad Association, and the world's first barrel-vaulted train station concourse, or "Grand Hall."

Over time, as tractive technologies evolved from steam to diesel and to diesel-electric powered engines, St. Louis Union Station too underwent countless changes. With the growing popularity of automobiles and aircraft as alternatives modes of transportation, St. Louis Union Station eventually fell into disuse by the late 1970s. In 1985, the complex was re-opened as a modern commercial center including a shopping complex.