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.
Santa Fe class 3460
In December 1937, locomotive #3461 set a world record for the longest single run by a steam locomotive by completing the from Los Angeles, California to Chicago without maintenance other than five refuelling stops en route, hauling Train #8, the Fast Mail Express. An average speed of was obtained, including stops; maximum speed during the run was . During steeply graded portions of the run it was, of course, assisted by helper locomotives. Such long distance runs were a goal of railway operating departments, enabling a reduction in locomotive numbers and through increased locomotive utilization, reduce overall costs.