Northern Pacific 7000, an F9 set, helps a westbound extra freight led by Northern Pacific 5120 up Bozeman Pass at Muir, Montana, in May 1954. Photo by J.M. Fredrickson. Other Subject Classes: diesel locomotive, helper locomotive, wood caboose.

Northern Pacific 7000, an F9 set, helps a westbound extra freight led by Northern Pacific 5120 up Bozeman Pass at Muir, Montana, in May 1954. Photo by J.M. Fredrickson. Other Subject Classes: diesel locomotive, helper locomotive, wood caboose.

Northern Pacific 7000, an F9 set, helps a westbound extra freight led by Northern Pacific 5120 up Bozeman Pass at Muir, Montana, in May 1954. Photo by J.M. Fredrickson. Other Subject Classes: diesel locomotive, helper locomotive, wood caboose.

Helper set Northern Pacific 857 and 858, both American Locomotive Company (Alco) RS-3s, help a westbound extra freight over Bozeman Pass near Muir, Montana, in June 1955. Photo by J.M. Fredrickson. Other Subject Classes: diesel locomotive, helper locomotive, steel caboose.

Helper set Northern Pacific 857 and 858, both American Locomotive Company (Alco) RS-3s, help a westbound extra freight over Bozeman Pass near Muir, Montana, in June 1955. Photo by J.M. Fredrickson. Other Subject Classes: diesel locomotive, helper locomotive, steel caboose.

Northern Pacific 2681, a class A-5, leads a westbound extra freight up Bozeman Pass at Muir, Montana, in September 1953. Photo by J.M. Fredrickson. Other Subject Classes: steam locomotive, freight train.

Northern Pacific 2681, a class A-5, leads a westbound extra freight up Bozeman Pass at Muir, Montana, in September 1953. Photo by J.M. Fredrickson. Other Subject Classes: steam locomotive, freight train.

Northern Pacific 5003, a class Z-5, helps a westbound extra freight led by Northern Pacific 2681 up Bozeman Pass at Muir, Montana, in September 1953. Photo by J.M. Fredrickson. Other Subject Classes: steam locomotive, helper locomotive, freight train.

Northern Pacific 5003, a class Z-5, waits at Muir, Montana after helping a train up Bozeman Pass before returning for its next assignment in September 1953. Photo by J.M. Fredrickson. Other Subject Classes: steam locomotive, helper locomotive.

Northern Pacific 5120, a Z-6, leads a westbound extra freight up Bozeman Pass near Muir, Montana, in May 1954. Photo by J.M. Fredrickson. Other Subject Classes: steam locomotive, freight train.