The City of Portland was a named passenger train operated by the Union Pacific Railroad and Chicago and North Western Railway between Chicago, Illinois, and Portland, Oregon. In 1935, the railroad dedicated the refurbished M-10001 streamliner trainset to power the train. In 1955 the Milwaukee Road assumed the service, replacing the Chicago and North Western between Chicago and Omaha. The train was discontinued May 1, 1971, with the inception of Amtrak. The route roughly follows the trail of the defunct Amtrak route, the Pioneer.
In addition to baggage, coach, and sleeping cars, during the mid-1950s the City of Portland added a dome coach, dome observation lounge and dome dining car to each consist. The dome dining cars were unique to Union Pacific and were only operated on this train and the City of Los Angeles. The dome cars were particularly popular as the train traveled along the scenic Columbia River, outside of Portland.