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.
GE steam turbine locomotives
The General Electric steam turbine locomotives were two steam turbine locomotives built by General Electric (GE) for Union Pacific (UP) in 1938. The two units were streamlined, in length, capable of producing , and reputedly able to attain speeds of . Stylistically, they resembled UP's Pullman-designed M-10003 through M-10006 power units and contemporary Electro-Motive Corporation (EMC) diesel designs.