The Great Northern S-1 was a class of 6 4-8-4 Northern type steam locomotives built by the Baldwin Locomotive Works in 1929 and operated by the Great Northern Railway until the late 1950s.
Should passenger trains exceed such a number of cars eastbound, helper service is added between Walton and Summit.
[3] Despite their overall success, they had a reputation for being hard on the rails.
When delivered, they were assigned for passenger service over the Divide between Havre and Whitefish, Montana, then in 1931, they were tested to pull freight between Whitefish, Montana and Hillyard, Washington.
The test was a success and the S-1s were reassigned to pull freight trains, leaving the passenger runs mainly to the later S-2 Class of 1930.