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The "GP7": Defining A New Era Of Railroading

Last revised:  December 16, 2024

By: Adam Burns

The GP7 began Electro-Motive's foray into the road-switcher market.  It was the builder's first, true such design and became a massive success.  From a historical perspective it was a landmark model, selling more than 2,700 examples in just a short five year production run. 

The GP7 witnessed more than twice the sales of Alco's RS3, the only other road-switcher with comparable success.  Its history began in 1948 when EMD unveiled its so-called "Branch Line" locomotive, the BL2.  

This interesting concept was a hybrid full width cab unit and road-switcher.  As the name implies it was intended to operate in branch line service, displacing aging steam engines on secondary corridors and completing dieselization for most railroads. 

Unfortunately, it found little interest and EMD ended production after only a year.   However, General Motors' subsidiary persevered, unveiling the GP7 in 1949 and all but completing EMD's dominance during the diesel's first generation era.

Photos

An Electro-Motive photo featuring GP7 demonstrator #100 in late 1949.

Overview

By the late 1940s, most railroads had acquired at least a few examples of road service diesels, if not completing dieselization altogether (Gulf, Mobile & Ohio).  Most, though, continued to operate some steam locomotives in secondary assignments well into the 1950s.

As Brian Solomon notes in his book, "EMD Locomotives," the standard F and E series models were not only expensive but also ill-suited for branch line work.  These lines usually contained many local customers, requiring a great of switching for which the cab units were ill-suited.

EMD's oddball BL2 was designed to do just that but failed to capture much interest.  Going back to the drawing board the builder unveiled the first in its General Purpose series in 1949, the GP7.  

This locomotive resembled road-switchers then being offered by Alco and Baldwin; an offset cab featuring a short hood at one end and long hood at the other.  These hoods were inset, allowing for walkways around the locomotive as well as improved sightlines from the cab.

Illinois Central GP7 #8900 works local service at Graymont, Illinois on February 19, 1958. Today, few traces of this line remain. Author's collection.

Design

Most railroads had no interest in spending so lavishly for diesels intended only secondary branch line service.  To enable complete dieselization, EMD designed the GP7 as cheaply as possible.  Spearheading the effort was EMD's chief engineer, Richard "Dick" Dilworth, who was instrumental in the development of the phenomenally successful FT. 

Rio Grande GP7 #5104 leads a string of livestock and boxcars southbound along U.S. 285 outside of Alamosa, Colorado during the 1950s. American-Rails.com collection.

Another key figure was John Markestein, who then headed EMD's styling department.  Dilworth began with the failed BL2.  He replaced the full length hood with a narrower design and off-set the cab, allowing for a short lead hood.   However, it carried its own stylish appearance with flush lines and tapering at each end. The roof line carried similar clean lines

Dubbed the "General Purpose" (GP) series, or 'Geep' for short, the GP7 debuted in October, 1949 when demonstrator #922 was unveiled.  The unit was later renumbered 100 and eventually sold to the Chicago & North Western as #1518.

Rio Grande GP7 #5108 is seen here at work in Pueblo, Colorado circa 1970. Robert Eastwood, Jr. photo. American-Rails.com collection.

To keep costs down, EMD incorporated as many redundancies into the model as possible, enabling the GP7 to perform practically any task from switching and branch line assignments to general road service.  In addition, the model was offered with an optional steam generator for passenger or commuter assignments. 

The locomotive's low cost enabled railroads to justify retiring their remaining steam locomotives.  Even holdouts like the Norfolk & Western acquired large rosters of General Purpose locomotives; the N&W purchased more than 300 GP9s between 1955-1959 and continued adding later variants throughout the 1960s.

Santa Fe GP7 #2758 and a CF7 in Temple, Texas, circa 1980. Mike Bledsoe photo. American-Rails.com collection.

In fact, the GP's practicality and redundancy suited railroads so well that EMD's once-popular streamlined models, which had sold thousands through the early 1950s, quickly fell out of favor.  The builder's F9 saw just 192 examples built for domestic railroads, and another 66 for Mexican and Canadian lines.

It's the early Erie Lackawanna era as a group of former Erie GP7s layover at the Magnolia Street Engine Terminal in Syracuse, New York during March, 1964. American-Rails.com collection.

The GP7 utilized EMD's standard prime mover at the time - also found in the popular F7 - the 16-cylinder, model 567B.  Internal components were also similar; a model D12B main generator, D27C traction motors, and Blomberg trucks.   The GP7 was offered in six different gear ratios, depending on a railroad's needs.

Missouri Pacific GP7 #1690 works local service at Austin, Texas on December 1, 1980. Mike Bledsoe photo. American-Rails.com collection.

Reception

EMD manufactured four demonstrators; #922 (renumbered 100), #200, #300, and #525 to tour the country, clad in an elegant blue and silver livery.

Sales for the locomotive took off quickly.  Interestingly, the Santa Fe even acquired five cabless GP7Bs in 1953.  This trend continued with the later GP9 with Union Pacific and Pennsylvania acquiring 165 examples "B" units.

Rock Island GP7 #1278 lays over at the small engine house in Peoria, Illinois, circa 1955. American-Rails.com collection.

The ruggedness and reliability of EMD's 567 engine block saw GP7s remain in service on many Class 1 systems for decades.  Some roads, like the Santa Fe and Illinois Central, carried out extensive rebuild programs to extend the lives of these locomotives for several more years.

Interestingly, these rebuilds can still be found in service today on short lines.  In addition, there are some standard GP7s still handling freight assignments while numerous others have been preserved at museums and heritage railroads.

Data Sheet

Production Roster

Total Built = 2,729

* Equipped with a GP9 carbody and 1,350 horsepower.

Reused Serial Numbers

Export

General Motors Diesel (GMD)

GP7B

Total Built = 5

This slide had no information. I presume it was perhaps taken in early October, 1963 along with the others in this bunch. The former Lackawanna GP7 (#960) has been reassigned its Erie Lackawanna number (#1279). Also note the trailing RS3 (another former DL&W unit). Author's collection.

Sources

• Foster, Gerald. A Field Guide To Trains. New York: Houghton Mifflin, 1996.

• Hayden, Bob. Diesel Locomotives: Cyclopedia, Volume 2 (Model Railroader). Milwaukee: Kalmbach Publishing Company, 1980.

• Marre, Louis A. Diesel Locomotives: The First 50 Years, A Guide To Diesels Built Before 1972.  Milwaukee: Kalmbach Publishing Company, 1995.

• Pinkepank, Jerry A. Diesel Spotter's Guide.  Milwaukee: Kalmbach Publishing Company, 1967.

• Solomon, Brian.  EMD Locomotives.  Minneapolis: MBI Publishing Company, 2006.

• Solomon, Brian.  GE and EMD Locomotives:  The Illustrated History.  Minneapolis:  Voyageur Press, 2014.