Intermountain 69202: EMD F7A Southern Pacific Black Widow Locomotives

The F7 was the fourth model in GM-EMD's successful line of F-unit locomotives, and by far the best-selling cab unit of all time. In fact, more F7s were built than all other F-units combined. The F7 succeeded the F3 model in GM-EMD's F-unit series, and was replaced in turn by the F9. Final assembly was at GM-EMD's La Grange, Illinois, plant or GMD's London, Ontario, facility. There was no F4, -5 or -6 model; "7" was chosen to match the contemporary twin-engine E7, and was also applied to the new GP7 road-switcher.

The F7 differed from the F3 primarily in internal equipment—mostly electrical—and some external features. Its continuous tractive effort rating was 20 percent higher, e.g. 40,000 lbf (180 kN) for an F7 with 65 mph (105 km/h) gearing, compared to 32,500 lbf (145 kN) for an F3 with the same gearing.

A total of 2,393 cab-equipped lead A units and 1,463 cabless-booster or B units were built.