Intended for fast passenger service, the S-2s were built lighter and with larger driving wheels than the earlier S-1 Class of Northerns of 1929. The design of the S-2 Class 4-8-4 was somewhat different from the traditional steam locomotive design on the Great Northern. The GN normally preferred to equip its engines with a Belpaire type boiler, but in an effort to reduce weight, the S-2's were delivered with a radial stay boiler. The S-2 came with a Vanderbilt type tender, which provided a capacity of 17,000 gallons of water and 5,800 gallons of oil. It was unique in being the only all-welded tender on the GN. This water-bottom tender had a Commonwealth cast-steel frame and rode on two 6-wheel cast steel trucks. The locomotives were fast but slippery when starting heavier trains. They were also the first class of 4-8-4 Northerns to be built with 80 inch driving wheels. They also proved to be reliable, as a single S-2 can haul up to 18 conventional steel passenger cars on westbound passenger runs, with helper service only necessary between Walton and Summit on eastbound runs, distance of 18 miles where the grade is 1.8%. They were also economical in fuel consumption and maintenance expenses, had an exceptionally high availability for service as well as being fast. Such positives had led the class to being excellent performers. All S-2s were delivered in the Cascade Green paint scheme except for No. 2577, which carried a coat of light grey or aluminum paint on the boiler and cylinder jackets at delivery, most likely for photographic purposes. It was eventually repainted in Cascade Green, matching the rest of the class. All engines came with chrome plated cylinder covers and steam chest heads and by the 1950s, all engines had received the more economical all-black paint scheme. The only major rebuilding of the class was the replacement of the original friction bearings with Timken roller bearings in the 1940s. Some engines were temporarily converted to burn coal for a period in the late 1930s. Vestibule cabs were added to engine 2577 in the early 1930s and engines 2582, 2586, 2587 and 2588 by the late 1940s.
Revenue service
The class spent most of their career pulling the Great Northern's passenger trains, such as the Empire Builder and the Oriental Limited between Chicago and Seattle, but have also pulled mail trains. They have also traversed over the famed Marias Pass. Because of their speed and reliability, the class has ran up to approximately 20,000 miles a month. By the late 1940s, the Great Northern had dieselized its premier passenger trains and the class were then assigned to lesser passenger runs and even freight service, of which the latter service proved unsuitable for the class due to the passenger design and by April of 1958, all of the S-2s have been retired.
Only one S-2 survived into preservation today, No. 2584. It was retired in December 1957 and on March 21, 1958, the Great Northern decided to hold it for historical purposes. On May 15, 1964, it was put on display at the Havre, MT depot, where she still resides today. The tender from S-2 No. 2575 also survives, it is currently used as an auxiliary tender for Spokane, Portland & Seattle 700.
