Rock Island's GP-7's were not equipped for suburban service, and so 1217 must be functioning as a switcher or pilot rather than the motive power for the whole train. That duty is probably going to revert to Alco RS--3 485 in due course. On the track to the left a pair of RS-3's are charging out of La Salle Street Station with another suburban train. Meanwhile, in the background, two New York Central EMD SW-1's are blocking mail and express cars into passenger and express train consists. Photo by Ken Crist, from my collection.
Several Chicago railroads, including Burlington, Chicago & Northwestern, Illinois Central, Milwaukee Road and Rock Island, provided extensive service to and from the Chicago suburbs.