One of the all-time great locos, the F7 was an upgrade of earlier F unit models. Packing 1500 horsepower, they were built in A (with control cab) and B (cabless booster ) unit configurations, so they could be MUed. Many were fitted with water tanks and steam generators for use in passenger service. Nearly 2,400 were purchased for use in the US, Canada and Mexico, and some remained in service until the 1980s.