In 1946, the Nickel Plate Road began the modernization of its passenger fleet with the purchase of the now-famous Bluebird Alco PA-1 diesels and new stainless steel coaches and sleepers.
At the same time, the NKP began shopping its diners, diner-lounges, and 80-series coaches at Stoney Island, IL, with the intent of upgrading its passenger service to post-war standards. With the opening of the Calumet, IL, shops in 1948, that rebuilding was moved to the new facility.
The Nickel Plate decided to enhance and expand express service in the new passenger fleet with the construction of ten light weight aluminum boxcars. Since the Frankfort, IN, shops had been upgrading older wooden boxcars with steel sides and new appliances since the end of World War II, this facility was chosen to build these new specialty cars from aluminum parts supplied by Railroad Division of Aluminum Company of America (ALCOA).
Built in 1947, these ten cars were engineered from an Advisory Mechanical Committee (AMC) design that was based on the standard A.R.A. 50-Ton boxcar. The use of the aluminum alloys in the construction of the cars produced a weight saving of approximately 8949 pounds versus the comparable steel prototype.
Additional modifications were made for service high-speed passenger trains, including the use of Timken roller bearings, and the addition of steam and air signal lines. Since the 8500 series cars did not have end doors, their service on passenger trains was limited to the head end, between the locomotives and the passenger cars, or the trailing at the rear of the train. The 8500-8509 cars provided the service for which they were built, but no additional express cars were ever needed or built.