The Union Pacific purchased the set in 1950 and assigned it to #457/458, its contribution to the pool service between Portland and Seattle along with Northern Pacific and Great Northern. UP's first "domeliner" normally ran with the four domes, several flat top coaches originally built for the Chicago-L.A. "Challenger" in 1937, and a Seattle through sleeper off the "City of Portland".

The service survived until the advent of Amtrak in May 1971, but the Train of Tomorrow domes had all disappeared long before. The dome coach, dome diner and dome sleeper were all scrapped, but the dome observation survived in a Pocatello, Idaho scrapyard for years until discovered and rescued. It is now under restoration in Ogden, Utah at the railroad museum there.