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 National still has many GP9RM locomotives in operation, as of 2016. Canadian Pacific had many GP9u locomotives in operation; however, they were all retired in 2015.
Several GP9s were rebuilt with a 1,500 horsepower (1.12 MW) CAT 3512 and re-classified as GP15C.
Several GP9 locomotives have been preserved at various railroad museums and as "park engines." The Western Pacific Railroad Museum at Portola, California rosters three of these units: Western Pacific Railroad 725 and 731, as well as Southern Pacific Railroad 2873, still painted in the Southern Pacific Santa Fe Railroad merger scheme. SP 2873 is a popular locomotive in the museum's Run a Locomotive program. There is also one on display at the Horseshoe Curve, Pennsylvania Railroad No. 7048. No. 7048 replaced K4s Pacific #1361 which in 1986 was removed from the site and rebuilt to haul excursion trains.
The Northwestern Pacific Railroad rosters an ex-Burlington Northern GP9, now in the NWP's "Bloody Nose" paint scheme, for mainly switching and MOW operations in Northern California. The Buffalo & Pittsburgh Railroad operates a former N&W GP9, now numbered 626. Its home yard is the Bradford, PA yard. The California Western Railroad, better known as the "Skunk Train," has three GP9s in their fleet. The Santa Maria Valley Railroad operates a former Milwaukee Road GP9 numbered 1801.
In the mid 1980s to early 1990s Guilford Rail System (now Pan Am Railways) started painting and renumbering their GP9 fleet into the Guilford Transportation scheme with the Springfield Terminal name on the side. Pan Am Railways still rosters 6 of the 50 GP9s that are left, the rest either having been scrapped or sold. The last 6 GP9s still rostered on PAR are 51, 52, 62, 71, 72, and 77. The 77 was painted into the Boston and Maine maroon and gold "Minuteman" scheme for Pan Am's heritage fleet, and the 52 was painted in the Maine Central green scheme.
The Hartwell Railroad operates former Chicago and North Western GP9 4556, née Chicago, Rock Island and Pacific 1315.
The Vintage Locomotive Society currently operates two GP9 locomotives: No. 4138 was built by General Motors Diesel (GMD) in November 1958 for the Grand Trunk Western (which eventually became part of Canadian National Railway). It was donated by CN to the Society in August 2002. 4138 is used on the Prairie Dog Central Railway in regular service and in some charter service. It acts as backup power should steam locomotive No. 3 be unavailable. No. 1685 was built by General Motors Diesel (GMD) in March 1957 for the Midland Railway Company of Manitoba as locomotive No. 2 (which became Burlington Northern Manitoba Limited No. 2, then BNSF No. 1685). It was donated to the Society by BNSF in July 2010. 1685 is used on the Prairie Dog Central Railway in regular service and in some charter service. It also acts as backup power should steam locomotive No. 3 or 4138 be unavailable.
CN still has a strong fleet of GP9 locomotives in service, designated as GP9RM, which were rebuilt in the 1980s. They use the following number series: 4000s, 4100s, 7000s, and 7200s.
Other operators include:Butte, Anaconda and Pacific Railway
Central Montana Rail (ex. Great Northern, still operate high nose, long-hood forward)
Montana Rail Link
Montreal, Maine and Atlantic Railway - ex-Bangor and Aroostook Railroad and ex-Canadian Pacific Railway
Adrian & Blissfield Railroad
Leadville, Colorado and Southern Railroad
Ontario Northland Railway
Grafton & Upton Railroad
Essex Terminal Railway (ETL)