Denver Union Station is the main railway station and central transportation hub in Denver, Colorado. It is located at 17th and Wynkoop Streets in the present-day LoDo district and includes the historic station house, a modern open-air train shed, a 22-gate underground bus station, and light rail station. A station was first opened on the site on June 1, 1881, but burned down in 1894. The current structure was erected in two stages, with an enlarged central portion completed in 1914.

The California Zephyr is a long-distance passenger train operated by Amtrak between Chicago and the San Francisco Bay Area, via Omaha, Denver, Salt Lake City, and Reno. At 2,438 miles (3,924 km), it is Amtrak's longest daily route, and second-longest overall after the Texas Eagle's triweekly continuation from San Antonio to Los Angeles, with travel time between the termini taking approximately 511⁄2 hours. Amtrak claims the route as one of its most scenic, with views of the upper Colorado River valley in the Rocky Mountains, and the Sierra Nevada. The modern train is the second iteration of a train named California Zephyr; the original train was privately operated and ran on a different route through Nevada and California.