In 2012, the station underwent a major renovation transforming it into the centerpiece of a new transit-oriented mixed-use development built on the site's former railyards.

The Kansas City architectural firm of Van Brunt & Howe was hired to design a larger replacement depot in the Romanesque Revival style.

[8] On July 4, 1906, a large arch was dedicated in front of the station in order to provide a symbolic threshold for travelers entering and leaving the city.

[9] 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 and Santa Fe, the Chicago, Burlington and Quincy, the Chicago, Rock Island and Pacific, the Colorado & Southern, the Union Pacific and the Denver & Rio Grande Western railways).

[11] Amtrak eventually became the sole provider of rail service through the station, operating only two trains daily between Chicago and the Bay Area with the California Zephyr.

[15][16][17] In 2001, the Regional Transit District (RTD), in partnership with the City of Denver and the State of Colorado bought the station and the 19 acres it sat on.

In 2004, the Fast Tracks tax increase passed which provided the funding needed to complete a new regional commuter station at site.

In 2012, construction began on a major renovation of the historic building transforming it into the centerpiece of a new transit-oriented mixed-use development built on the site's former railyards.

[6][18] In 2008, Hargreaves Associates and Skidmore, Owings & Merrill were selected to design the public spaces including the landscape, train hall, bus terminal, and light rail station.

[29][30] By 2012, RTD selected the proposal from the Union Station Alliance to renovate the structure as a hotel at a cost of $54 million with retail, public, and transit facilities and approved a 99-year lease for its redevelopment.

The train hall stands immediately behind the historic building and houses tracks for Amtrak and the commuter rail lines.

Street-level pavilions at the light rail stop/Chestnut Place, Wewatta Street and at each platform in the train hall provide additional vertical circulation to the bus terminal.

The wing buildings were built with the first 1881 structure in a Romanesque Revival style, featuring tall, narrow windows, rusticated stonework and motifs of Colorado's state flower, the columbine.

They originally functioned as offices and other facilities for the station through its history, although today the structures house guestrooms for the Crawford Hotel and several restaurants.

When originally constructed, the Great Hall also included three large chandeliers and ten long wooden benches that incorporated heating and lighting into their framework.

The old ticket counters and offices were also converted into the Terminal Bar along with several retail and restaurant spaces being created on the periphery of and opening on to the Great Hall.