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.
Chessie (train)
To pull the "Chessie" the C&O ordered three experimental steam turbine locomotives from the Baldwin Locomotive Works. As diesel locomotives became more prevalent following World War II, the C&O was one of several railroads loath to abandon coal as a fuel source, and saw steam turbine technology as a possible alternative to diesel. At the time of their construction these locomotives were the longest single-unit locomotives in the world. Not including research and development, the three locomotives cost . The M1s proved a failure in operation and were scrapped in 1950.