The F7s are major contenders for the fastest steam locomotives ever built, as they ran at over 100 miles per hour (160 km/h) daily.

One run in January 1941 recorded by a reporter for Trains magazine saw 110 miles per hour (180 km/h) achieved twice—in the midst of a heavy snowstorm.

In 1939, shortly after they were introduced into passenger service, the Twin Cities Hiawatha schedule was modified such that the engines would need to run the 78.3 mi (126.0 km) between Portage and Sparta, Wisconsin in 58 minutes—a start-to-stop average of 81 mph (130 km/h).

[1] In the late 1940s, the Milwaukee F7s were modified to equip an additional Mars Light above the original single highlight to further enhance the safety of daily highspeed operation.

The engine was severely damaged, broken drive gear tore up ties and roadbed, and debris (including the main rod) was found as far as 1400 feet west of Edgebrook Station.