Northern Pacific 50-foot, box car number 5211 with plug and sliding doors is on a siding at Boulder, Colorado, on February 14, 1965. Photo by GJ Werkema. Other subject classes: freight car, steel box car

Northern Pacific 40.5-foot, box car number 8130 with plug and sliding doors is on a siding at Denver, Colorado, on June 6, 1978. The car is part of the 8000-8449 number series. Photo by GJ Werkema. Other subject classes: freight car, steel box car