A notable feature of the 1936 version of the train was the "Frontier Shack" tavern, which had the feel of a Western saloon.

The infrequent departure schedule led Union Pacific to advertise a train's "sailings", as though it were an ocean liner.

[5][6] While as fast as the City of Denver, the three-car sets in no way compared to amenities aboard the 12-car Union Pacific streamliners,[7] which included the "Frontier Shack" tavern, a dining-cocktail lounge, and a sleeper-lounge-observation car.

[7] Fulfilling its early promise, the City of Denver traveled at an average speed of 66 miles per hour (106 km/h), the fastest of the Union Pacific's streamliners.

Even as it upgraded and replaced its other streamliners, Union Pacific kept the original trainsets on the route until 1953, finally introducing new lightweight equipment in 1953–1954.

Having none of its own, the Union Pacific leased two all-roomette Pennsylvania Railroad sleeping cars and billed it as "Slumbercoach service.

"[14] Throughout the late 1950s and 1960s the Union Pacific gradually downgraded its passenger services and consolidated trains as losses mounted.

[15] On September 7, 1969, the Union Pacific combined five of its Chicago–West Coast streamliners into a single massive train dubbed by critics the "City of Everywhere."

In March 1950 it made the following stops west of Omaha: Columbus, Grand Island, Kearney, and North Platte in Nebraska and Julesburg in Colorado.

On the C&NW it made the following stops west of Chicago, all in Iowa: Cedar Rapids, Ames, Boone, and Council Bluffs.

In June 1960 the City of Denver stopped in Davis Junction (for Rockford) and Savanna in Illinois, Marion (for Cedar Rapids) and Perry in Iowa.

[18]: 742 Pullman-Standard and the Electro-Motive Corporation collaborated on the M-10005 and M-10006 streamlined trainsets which served as the City of Denver's original equipment.

[8] The 50-seat coaches featured 2x2 seating, with baggage racks in the vestibule end and separate men's and women's restrooms in the other.

[19] The two trainsets remained in use until March 19, 1953, when the Union Pacific introduced conventional lightweight equipment powered by EMD locomotive sets.