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.
Steam locomotive
The most-manufactured single class of steam locomotive in the world is the 0-10-0 Russian locomotive class E steam locomotive with around 11,000 produced both in Russia and other countries such as Czechoslovakia, Germany, Sweden, Hungary and Poland. The Russian locomotive class O numbered 9,129 locomotives, built between 1890 and 1928. Around 7,000 units were produced of the German DRB Class 52 2-10-0 Kriegslok.
The British GWR 5700 class numbered about 863 units. The DX class of the London and North Western Railway numbered 943 units, including 86 engines built for the Lancashire and Yorkshire Railway.