While EMD's E-units were successful passenger engines, their A1A-A1A wheel arrangement made them less useful in mountainous terrain. Several railroads had tried EMD's F3 in passenger service, but there was insufficient water capacity in an A-unit fitted with dynamic brakes. The Atchison, Topeka and Santa Fe Railway's solution was to replace the steam generators in A-units with a water tank, and so only fitted steam generators into the B-units. The Northern Pacific Railway's solution was to fit extra water tanks into the first baggage car, and to pipe the water to the engines. The real breakthrough came when EMD recognized the problem and added the stretched FP7 to its catalog. s with the San Francisco Zephyr at Yuba Gap, 1975 A total of 381 cab-equipped lead A units were built; unlike the freight series, no cabless booster B units were sold. Regular F7B units were sometimes used with FP7 A units, since they, lacking cabs, had more room for water and steam generators. The FP7 and its successor, the FP9, were offshoots of GM-EMD's highly successful F-unit series of cab unit freight diesels. F3s, F7s, and F9s equipped for passenger service are not FP-series locomotives, which, although similar in appearance, have distinctive differences. This includes, but not limited to, the greater body length. The extra of length was added behind the first body-side porthole, and can be recognised by the greater distance between that porthole and the first small carbody filter grille. The corresponding space beneath the body, behind the fronttruck, was also opened up; this either remained an empty space or was filled with a distinctive water tank shaped like a barrel mounted transversely. Note that over their production run, there were numerous detail changes including the style of side grills, carbody louvres, and dynamic brake fan sizing. Some railroads such as Southern Pacific and Canadian Pacific outfitted their units with rooftop-mounted icicle breakers for protecting dome car windows in mountain territory where icicles formed around the roofs of tunnels.
Clinchfield Railroad , renumbered as Western Maryland Railway 67, in working condition and in use at the Durbin and Greenbrier Valley Railroad.
Milwaukee Road 96C, in Monon livery, inoperable at the former Indiana Transportation Museum in Noblesville, Indiana. As of September 10, 2019, the locomotive is up for final auction and will be scrapped if not auctioned off by September 11.
Milwaukee Road 101A, on static display in Cresco, Iowa.
Southern Railway 6141 and 6138 as R J Corman 1940-1941 in use by the operation out of Bardstown, Kentucky.
Western Pacific 805-A, a locomotive used on the famous California Zephyr, is preserved in operable condition at the Western Pacific Railroad Museum at Portola, California.
