GM&O Alco RS21 59 switches the Bloomington, Illinois yard in April 1958. The unit, formerly Alton Route 59, was built in 1945 and retired in 1974. The box-like appliance with the stack just ahead of the cab is an oil-burning heater to keep the engine crankcase oil warm, allowing the engine to be shut down in cold weather; three GM&O Alco road switchers, including No. 50 on the preceding page, had this device.