Milwaukee Road class F7
The F7s are major contenders for the fastest steam locomotives ever built, as they ran at over daily. One run in January 1941 recorded by a reporter for "Trains" magazine saw achieved twice—in the midst of a heavy snowstorm. Baron Gérard Vuillet, a French railroading expert, once recorded a run between Chicago and Milwaukee where the locomotive reached and sustained an average for . However, the British locomotive LNER Class A4 4468 "Mallard" is officially accepted to be the world's fastest, with a run recorded at but authenticated at 126 mph in 1938.
Metropolitan Railway electric locomotives
The second ten, also constructed by Metropolitan Amalgamated, were built to a box car design with British Thompson Houston control equipment. These locomotives weighed 47 tons, and were long over buffers and entered service in 1907. The control equipment was replaced with the Westinghouse type in 1919.
In the early 1920s, the Metropolitan placed an order with Metropolitan-Vickers of Barrow-in-Furness for rebuilding the twenty electric locomotives. When work started on the first locomotive, it was found to be impractical and uneconomical and the order was changed to building completely new locomotives using some equipment recovered from the originals. The new locomotives were built in 1922-1923 and weighing 61½ tons, they had four motors, giving a one-hour rating of and a top speed of .