Northern Pacific 4025, a class Z-3, leads an eastbound extra freight on the Milwaukee mainline between Haugan and Saint Regis, Montana, on May 28, 1952. Photo by J.M. Fredrickson. Other Subject Classes: steam locomotive, freight train, river.

Northern Pacific 4025, a class Z-3, leads an eastbound extra freight on the Milwaukee mainline between Haugan and Saint Regis, Montana, on May 28, 1952. Photo by J.M. Fredrickson. Other Subject Classes: steam locomotive, freight train, river.

Northern Pacific 4025, a class Z-3, leads an eastbound extra freight downhill from the summit of Lookout Pass west of Haugan, Montana, on May 28, 1952. Photo by J.M. Fredrickson. Other Subject Classes: steam locomotive, freight train, river.

Northern Pacific 4025, a class Z-3, leads an eastbound extra freight downhill from the summit of Lookout Pass west of Haugan, Montana, on May 28, 1952. Photo by J.M. Fredrickson. Other Subject Classes: steam locomotive, freight train, river.

Northern Pacific 4025, a class Z-3, leads an eastbound extra freight downhill after reaching the summit of Lookout Pass, Montana, on May 28, 1952. Photo by J.M. Fredrickson. Other Subject Classes: steam locomotive, freight train.

Northern Pacific 4025, a class Z-3, hauls an eastbound extra freight up the 4 percent grade and reaches the summit of Lookout Pass, Montana, on May 28, 1952. Photo by J.M. Fredrickson. Other Subject Classes: steam locomotive, freight train.

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 4025, a class Z-3, leads an eastbound extra freight through Mullan, Idaho, east of Wallace, on May 28, 1952. Photo by J.M. Fredrickson. Other Subject Classes: steam locomotive, freight train.

Northern Pacific 4025, a class Z-3, leads an eastbound extra freight on the Milwaukee mainline between Haugan and Saint Regis, Montana, on May 28, 1952. Photo by J.M. Fredrickson. Other Subject Classes: steam locomotive, freight train, river.

Northern Pacific 4025, a class Z-3, leads an eastbound extra freight across a short bridge on the Milwaukee mainline between Haugan and Saint Regis, Montana, on May 28, 1952. Photo by J.M. Fredrickson. Other Subject Classes: steam locomotive, freight train, plate girder bridge.