The M-10000 was an early American streamlined passenger trainset that operated for the Union Pacific Railroad from 1934 until 1941. It was the first streamlined passenger train to be delivered in the United States, and the second to enter regular service after the Pioneer Zephyr of the Chicago, Burlington and Quincy Railroad. The performance of the Railplane in testing drew the attention of Union Pacific, who sought the services of Pullman-Standard in building a small, lightweight streamlined trainset for mainline service. Union Pacific ordered M-10000 from Pullman in May 1933 at a cost of $230,997, following an analysis of passenger traffic that concluded new, more cost effective equipment than heavyweight passenger cars and steam locomotives was required for maintaining profitability, especially on low-traffic routes. The power car measured long, followed by coaches measuring and . The two passenger coaches each had a capacity of 60 people; the last coach also included a small galley at the rear end to prepare meals that were served at passengers' seats. The popular train was put on display at the 1934 World's Fair ("A Century of Progress") in Chicago from May 26 to October 31, 1934. It was somewhat overshadowed by the other lightweight streamliner, the diesel-powered Burlington Zephyr, which entered the fair after a record-setting "Dawn to Dusk Dash" speed run from Denver to Chicago, in time to arrive at the "Wings of a Century" transportation pageant. During its testing, demonstration, and display periods, the M-10000 trainset included the sleeper car Overland Trail, which was removed from the consist prior to revenue service and added to Union Pacific's next streamliner, M-10001.
M-10000 was placed in revenue service between Kansas City, Missouri and Salina, Kansas as The Streamliner on January 31, 1935. It was subsequently named City of Salina as Union Pacific adopted the "City of..." convention for its new streamliners, but was also nicknamed the "Tin Worm" or "Little Zip".