Chicago Union Station is a major railroad station that opened in 1925 in Chicago, Illinois, replacing an earlier station built in 1881. It is the only remaining intercity rail terminal in Chicago, as well as being the city's primary terminal for commuter trains. The station stands on the west side of the Chicago River between West Adams Street and West Jackson Boulevard, just outside the Chicago Loop. Including approach and storage tracks, it is about nine and a half city blocks in size.