The initial design for the station was created in 1882 by McKim, Mead, and White.
 Had the original plan been built, the station would have been the largest train station in the world.
 A smaller plan was introduced by architects Van Brunt & Howe, and accepted in 1885.
 Construction of the station began in 1890.
It was built by Northern Pacific Terminal Company 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.
Neon signs were added to the tower in 1948.
The signs read "Go by Train" on the northeast and southwest sides and "Union Station" on the northwest and southeast sides.

The station was placed on the National Register of Historic Places in 1975.

The neon signs on the tower went dark in March 1971, because the railroads using it, Union Pacific, Burlington Northern and Southern Pacific, were preparing to transfer all of their remaining passenger services to Amtrak.
For that reason, the station's then-owner, the Portland Terminal Railroad (itself jointly owned by those three railroads), decided to discontinue operation of the signs.
 In 1985, two local non-profit groups, the National Railway Historical Society (Pacific Northwest chapter) and the Oregon Association of Railway Passengers, led a fundraising campaign for public donations to enable the signs to be restored to operation.
 New neon tubes, in place of the old, were installed in July, and the signs were switched back on and returned to regular use in September 1985.
 The "Union Station" signs remain illuminated continuously, while the "Go by Train" signs flash on and off, in a sequence of "Go", then "Go by", then all three words, then off and on and repeat.

In 1987, ownership of the station and surrounding land was transferred from Portland Terminal Railroad to the Portland Development Commission (now Prosper Portland) 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.
The initial design for the station was created in 1882 by McKim, Mead, and White.  Had the original plan been built, the station would have been the largest train station in the world.  A smaller plan was introduced by architects Van Brunt & Howe, and accepted in 1885.  Construction of the station began in 1890. It was built by Northern Pacific Terminal Company 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. Neon signs were added to the tower in 1948. The signs read "Go by Train" on the northeast and southwest sides and "Union Station" on the northwest and southeast sides.
The station was placed on the National Register of Historic Places in 1975.
The neon signs on the tower went dark in March 1971, because the railroads using it, Union Pacific, Burlington Northern and Southern Pacific, were preparing to transfer all of their remaining passenger services to Amtrak. For that reason, the station's then-owner, the Portland Terminal Railroad (itself jointly owned by those three railroads), decided to discontinue operation of the signs.  In 1985, two local non-profit groups, the National Railway Historical Society (Pacific Northwest chapter) and the Oregon Association of Railway Passengers, led a fundraising campaign for public donations to enable the signs to be restored to operation.  New neon tubes, in place of the old, were installed in July, and the signs were switched back on and returned to regular use in September 1985.  The "Union Station" signs remain illuminated continuously, while the "Go by Train" signs flash on and off, in a sequence of "Go", then "Go by", then all three words, then off and on and repeat.
In 1987, ownership of the station and surrounding land was transferred from Portland Terminal Railroad to the Portland Development Commission (now Prosper Portland) 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.
Portland Union Station