This strange flat-faced machine was one of two unique AB6 diesels built by EMD in 1940 for the Rock Island. Basically modified E6 B-units with cabs, they were designed to run as trailing units on the Rocky Mountain Rocket and then handle the train's Colorado Springs section alone. They spent their later years in commuter service, as RI 750 was doing on an August 1969 night at the old LaSalle Street Station.
Several Chicago railroads, including Burlington, Chicago & Northwestern, Illinois Central, Milwaukee Road and Rock Island, provided extensive service to and from the Chicago suburbs.
