The Milwaukee Road used two for passenger service, designated class EP-4 (2-D+D-2), and the remaining ten for freight, designated class EF-4. They were used on the railroad's electrified Rocky Mountain Division in Montana and Idaho to take the place of older GE boxcab electrics that had been operating there since the 1920s. They were never used on the road's electrically disjunct Coast Division in Washington, as none of that division's substations were upgraded to accommodate them. Three had been delivered in standard gauge, while the rest were converted to standard gauge in the Milwaukee's shops.