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.
Mallet locomotive
Mallet designs were popular in Hungary, too. 30 of (B'B) were built between 1898–1902 (the last one served until 1958). was a (1B)B locomotive in service between 1905–1969 and (C'C) until 1962. The strongest Mallet-locomotive of the Hungarian State Railways was MÁV 601, a (1'C)C type steam locomotive. With 2200 kW power, MÁV 601 was the most powerful steam locomotive built before and during the First World War in Europe.