The lead architect was Asa Beebe Cross, who "adorned the exterior of the building with intricate towers of varying heights, arched windows framed in stone and rows of dormers projecting from the steeply pitched mansard roof".

[5] In 1903, the lack of room for expansion and a major flood[6] led the city and the railroads to decide a new station was required.

There are three chandeliers weighing 3,500 pounds (1600 kg) each, and the Grand Hall clock face is 6 feet (1.8 m) in diameter.

[8] The building's scale reflects Kansas City's central location as a hub for both passenger and freight rail traffic.

[8] The Kansas City massacre occurred on June 17, 1933, in front of Union Station, while captured fugitive Frank Nash was to be delivered to prison via train.

The massacre highlighted the lawlessness of Kansas City under the Pendergast Machine and resulted in the arming of all FBI agents.

Operating costs are funded by general admission and theater ticketing, grants, corporate and private donations, commercial space leases, and facility rental.

[12] Union Station hosts Science City (opened in 1999), a family-friendly interactive science center with more than 50 hands-on exhibits;[13] the H&R Block City Stage Theater, a live-action venue with productions for all ages; the Regnier Extreme Screen, the largest movie screen in the region at five and half stories tall; two restaurants, including Pierponts, an upscale steak and seafood restaurant, and Harvey's; many shops; the Gottlieb Planetarium, the largest planetarium in the area; and various temporary museum exhibits including Dead Sea Scrolls in 2007, Bodies Revealed in 2008, Dialog in the Dark in 2009, Dinosaurs Unearthed in 2010 and Diana, A Celebration focusing upon Princess Diana in 2011.

[15] In April 2015 and 2017, the reality TV show American Ninja Warrior was filmed at Union Station.

On February 14, 2024, another mass shooting occurred in front of Union Station immediately after the Super Bowl LVIII victory parade and rally honoring the Kansas City Chiefs.

Of the twelve Missouri stations served by Amtrak, Kansas City was the second busiest in the 2015 fiscal year, boarding or disembarking an average 421 passengers daily.