The EMD F7 was a 1,500 horsepower B-B Diesel-electric locomotive produced between February, 1949 and December, 1953 by General Motors' Electro-Motive Division. It succeeded the F3 model in GM-EMD's F-unit sequence, and was replaced in turn by the F9. Final assembly was at GM-EMD's La Grange, Illinois plant. Although originally promoted as a freight-hauling unit by EMD, the F7 was also used in passenger service hauling such trains as the Santa Fe's El Capitan.
A total of 2,366 cab-equipped lead A-units and 1,483 cabless booster or B-units were built. The F7 was the fourth model in GM-EMD's highly successful F-unit series of cab unit locomotives, and was, prior to the introduction of the EMD SD40-2 freight unit, the best selling Diesel-electric locomotive of all time.
Many F7s remained in service for decades, as railroads found them economical to operate and maintain. However the locomotive was not very popular with the yard crews who operated them in switching service, due to the fact that they were difficult to mount and dismount, and it was also nearly impossible for the engineer to see hand signals from his ground crew without leaning way outside the window. As most of these engines were bought and operated before two-way radio became standard on most American railroads, this was a major point of contention. In later years, with the advent of the "GP" type "road switchers", Fs were primarily used in "through freight" and "unit train" service where there was very little or no switching to be done on line of road.
The F7 can be considered the zenith of the cab unit freight Diesel, as it was ubiquitous on North American railroads until the 1970s (longer in Canada). The F7 design has become entrenched in the popular imagination due to it having been the motive power of some of the most famous trains in North American railroad history.
The F7 replaced the F3, differing primarily in internal equipment (mostly electrical) and some external features. The F7 was eventually succeeded by the more powerful but mechanically similar F9.