The SD7 was General Motors Electro-Motive Division’s first foray into 6-axle power. The “SD” stood for Special Duty, while the 7 was carried over for the 4-axle GP7 series. This new series of locomotives provided extra tractive effort spread and weight distribution across the six-axle trucks. Production lasted from May of 1951 to November of 1953. A total of 188 units were built for 17 railroads, from class Is to industrial operations. The SD7 would give way to the SD9.

In January of 1954, the first SD9 rolled off the assembly line with production lasting until June of 1959, after 471 examples were built for North American roads with another 44 going to export operations. The SD9 was similar to the SD7, but featured an upgraded 567C prime mover and distinctive class lights, pointed on an angle outwards whereas the SD7 was more prominent towards the center of the nose. The SD7 and the SD9 were also used as a base for rebuilds such as the SD10.

In the mid-1970s, Milwaukee Road looked for a way to extend the life of their SD7 and SD9 locomotives. Most of the SD7s and four SD9s were cycled through Milwaukee Road’s Milwaukee Shops to be rebuilt. Notable features included the addition of Horst paper air filters, four-stack exhausts and the high hood being chopped down with a rounded short-nose style cab. These could be found working in Chicago all the way to the western end of Milwaukee in Seattle. They also lasted through the SOO Line right on into CP Rail.

The Rapido Trains HO scale EMD SD7, SD9 and SD10 Locomotive features:

• Measured from a living SD9
• Road-specific details for each model variant
• Separate grab irons and handrails installed at the factory
• Operating headlights, rear lights, white class lights AND beacons (where appropriate).
• Highly detailed cab interior
• Correct fuel and water tank arrangements per road
• Multiple styles of stepwells
• See-through, etched steps
• High short hood and modified ‘chopped’ short hood where appropriate
• Appropriate cab or nose headlights
• Multiple dynamic-brake hatches
• DC/Silent (21-pin DCC Ready) or DC/DCC/ESU LokSound
• And much, much more!