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 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.