An EMD GP9 is a four-axle diesel-electric locomotive built by General Motors’ Electro-Motive Division in the United States, and General Motors Diesel in Canada between January, 1954, and August, 1963. US production ended in December, 1959, while an additional thirteen units were built in Canada, including the last two in August, 1963. Power was provided by an EMD 567C sixteen-cylinder engine which generated 1,750 horsepower (1.30 MW). This locomotive type was offered both with and without control cabs; locomotives built without control cabs were called GP9B locomotives. All GP9B locomotives were built in the United States between February, 1954, and December, 1959.
A total of 3,441 units of this locomotive model were built for American railroads, with an additional 646 for Canadian railroads and 10 for Mexican railroads. 5 units were built for a railroad in Brazil, 4 units were built for a railroad in Peru and 6 units were built for a railroad in Venezuela. Of the GP9B, 165 examples were built for American railroads.
There were 40 GP9M units built that are included in the 3,441 units built for United States railroads. A GP9M was built with parts from another older EMD locomotive, either an F unit or a damaged GP7. The use of parts from these older locomotives caused the GP9Ms to have a lower power rating than a GP9. This would be either 1,350 horsepower (1.01 MW) if the donor locomotive was an FT/F2 or 1,500 horsepower (1.12 MW) from F3/F7/GP7 locomotives.
Many rebuilt GP9s remain in service today with shortline railroads and industrial operators. Some remain in rebuilt form on some major Class I railroads, as switcher locomotives. Canadian Pacific Railway and Canadian National Railway still have many in their fleets in 2012 as switcher locomotives.
Several GP9s were rebuilt with a 1,500 horsepower (1.12 MW) CAT 3512 and re-classified as GP15C.