The initial design for the station was created in 1882. Had the original plan been built, the station would have been the largest train station in the world. A smaller plan was introduced in 1885. Construction of the station began in 1890. It was built at a cost of $300,000, and opened on February 14, 1896.
The signature piece of the structure is the 150 ft. tall Romanesque Revival clock tower. The neon signs were added to it in 1948. The signs read “Go by Train” on the northeast and southwest sides and “Union Station” on the northwest and southeast sides.
In 1987, ownership of the station and surrounding land was transferred from Portland Terminal Railroad to the Portland Development Commission as part of the Downtown/Waterfront urban renewal district. Shortly afterwards, Union Station underwent a renovation. It was rededicated in 1996.
In 2004, the roadway in front of the station was reconfigured, providing a new connection to the northwest and a forecourt. In addition, the area is being redeveloped, including new housing where railroad tracks once were.