Northern Pacific steam locomotive 4021 at Missoula, Montana, on June 08, 1955. Number 4021 is a class Z-3 built by Alco-Brooks in 1920. Photo by J.M. Fredrickson. Other Subject Classes: steam locomotive in roster photo

Northern Pacific steam locomotive 4021 at Missoula, Montana, on June 08, 1955. Number 4021 is a class Z-3 built by Alco-Brooks in 1920 J.M. Fredrickson collection. Other Subject Classes: steam locomotive in roster photo

Northern Pacific steam locomotive 4021 at Missoula, Montana, on June 08, 1955. Number 4021 is a class Z-3 built by Alco-Brooks in 1920. Photo by J.M. Fredrickson. Other Subject Classes: steam locomotive in roster photo

Northern Pacific steam locomotive 4025 at Missoula, Montana, on June 08, 1955. Number 4025 is a class Z-3 built by Alco-Brooks in 1920. Photo by J.M. Fredrickson. Other Subject Classes: steam locomotive in roster photo

Northern Pacific (NP) 5100, the first class Z-6 locomotive delivered to the NP in 1936, passes the depot at Missoula, Montana, with an eastbound extra freight in 1953. Photo by J.M. Fredrickson. Other Subject Classes: steam locomotive, freight train, passenger depot.

Northern Pacific steam locomotive 5101 at Missoula, Montana, on September 02, 1953. Number 5101 is a class Z-6 built by Alco-Schenectady in 1936. Photo by J.M. Fredrickson. Other Subject Classes: steam locomotive, roster photo

Northern Pacific steam locomotive 5103 at Missoula, Montana, on August 19, 1943. Number 5103 is a class Z-6 built by Alco-Schenectady in 1936. Photo by J.M. Fredrickson. Other Subject Classes: steam locomotive, roster photo

Northern Pacific steam locomotive 5104 at Missoula, Montana, on August 19, 1943. Number 5104 is a class Z-6 built by Alco-Schenectady in 1936. Photo by J.M. Fredrickson. Other Subject Classes: steam locomotive, roster photo

Northern Pacific steam locomotive 5110 at Missoula, Montana, on August 20, 1943. Number 5110 is a class Z-6 built by Alco-Schenectady in 1936. Photo by J.M. Fredrickson. Other Subject Classes: steam locomotive, roster photo

Northern Pacific steam locomotive 5112 at Missoula, Montana, on August 20, 1949. Number 5112, a class Z-6 built by Alco-Schenectady in 1937, is on the turntable at the roundhouse. Photo by J.M. Fredrickson. Other Subject Classes: steam locomotive, turntable