In 1980, EMD released the GP50, one of the final models using the 645-model diesel engine. The GP50 used the new 16-cylinder 645F-series engine producing 3500 horsepower through the new AR-15 alternator. The AC electrical current from the alternator was rectified to DC current to power the four new D87 traction motors.

The first GP50s were fifty units built for Chicago & NorthWestern starting in May 1980. Seventy units for Southern, ten units for Missouri Pacific and ten units for Burlington Northern completed the first year’s production. Twenty more GP50s for Southern, an additional twenty for Missouri Pacific and thirty for Santa Fe were built in 1981.

In 1985, fifteen units went to the Santa Fe and 53 to Burlington Northern. These were Phase II versions with straight-sill frame and free-flow or “laundry chute” traction motor blower bulge. They were the last GP50s built, bringing the production total to 278 units.

Until the early 1990s, the GP50s on all five railroads could be found on almost any kind of mainline train and were mixed with that road’s other power. However, GP50s were often assigned in three or four unit sets to hotshot piggyback trains. Santa Fe and Southern also had GP50s equipped as masters for remote-control operations (distributed power in today’s terms). Santa Fe used theirs on coal trains out of New Mexico, while Southern used theirs on manifest trains on the CNO&TP between Cincinnati, Ohio and Chattanooga, Tennessee. In later years the GP50s migrated to general service including locals.

Many of these locomotives are now being rebuilt with ecologically sound emission control for higher population centers. A new era emerges as technology meets proven reliability for these EMD products.

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