Around the turn of the 20th century, the Kansas City Terminal Railway, a company controlled by the 12 railroads serving Kansas City, decided that a new location was needed for the train depot. The location at the time was prone to flooding by the Kansas and Missouri Rivers. A new location was selected south of the central business district, above and away from the floodplain. The architect chosen to design the building was Jarvis Hunt, a proponent of the City Beautiful movement. The design was a main hall for ticketing, and a perpendicular hall extending out over the tracks for passenger waiting. The Beaux-Arts station opened on October 30, 1914 as the second-largest train station in the country. The building encompasses 850,000 square feet (79,000 m²), the ceiling in the Grand Hall is 95 feet (29 m) high, there are three chandeliers weighing 3,500 pounds (1600 kg) each, and the Grand Hall clock has a six-foot (1.8-m) diameter face. Due to its central location, Kansas City was a hub for both passenger and freight rail traffic. The scale of the building reflected this status.
Union Station made headlines on June 17, 1933, as four unarmed FBI agents were gunned down by gang members attempting to free captured fugitive Frank Nash. Nash was also killed in the gun battle. The “Kansas City Massacre” highlighted the lawlessness of Kansas City under the Pendergast Machine and resulted in the arming of all FBI agents.
In 1945, annual passenger traffic peaked at 678,363. As train travel declined beginning in the 1950s, the city had less and less need for a large train station. By 1973, only 32,842 passengers passed through the facility, all passenger train service was now run by Amtrak, and the building was beginning to deteriorate. The city government of Kansas City wished to preserve and redevelop the building. To facilitate this, they made a development deal with Trizec, a Canadian redevelopment firm. Included in the deal was an agreement that Trizec would redevelop the station. Between 1979 and 1986, Trizec constructed two office buildings on surrounding property, but did not redevelop the station. In 1985, Amtrak moved all passenger operations to a smaller facility. By this time, the station was essentially closed. In 1988, the city filed suit against Trizec for the failure to develop the station; the case was settled in 1994. For most of this time period, the building continued to decay.
In 1996, residents in five counties throughout the metropolitan area in both Kansas and Missouri approved the so-called "bi-state tax", a 1/8th of a cent sales tax, part of which helped to fund just under half of the $250 million restoration of Union Station. Renovation began in 1997 and was completed in 1999. The remaining money was raised through private donations and federal funding.
Today Union Station receives no public funding. Current operating costs are funded by general admission and theater ticketing, grants, corporate and private donations, commercial space leases and facility rental. Union Station is a nonprofit 501c3 organization. Union Station is now home to Science City, a family-friendly interactive science center with more than 50 hands-on exhibits; the H&R Block City Stage Theater, a live-action venue with productions for young and old alike; the Reginer Extreme Screen, the largest I-werks 3-D movie screen in the region at five and half stories tall; two restaurants, including Pierponts, an upscale Steak and Seafood restaurant, and the Harvey House Diner, a 50s style tribute to the restaurants once owned and operated by Fred Harvey; retail shops, including the Station Master gift shop; the Gottlieb Planetarium, the largest planetarium in the area; and various temporary museum exhibits including the internationally acclaimed Dead Sea Scrolls in the spring of 2007, Bodies Revealed from February 29 - September 1, 2008, and Dialog in the Dark. Also the Irish Museum and Cultural Center is located in the station since March 17, 2007.
In 2002, Amtrak restored passenger train service to the station. There are currently two trains daily to and from St. Louis, two trains daily to Chicago, and one train daily to the southwest (ultimately, to Los Angeles).