The locomotives were built to haul passengers on the GN mainline, pulling the Empire Builder and the Oriental Limited and were assigned to the Montana division for service between Williston, North Dakota and Havre, Montana and the Spokane division for service between Spokane, Washington and Wenatchee, Washington, then assigned to the Divide between Havre and Whitefish, Montana, of which mostly runs through the famed Marias Pass, though they were also used on GN tracks outside of their assigned areas.