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.
Race to the North
On the East Coast route, GNR locomotives ran on what was undoubtedly the fastest line in the world but the ""Flying Scotsman"" service was not their fastest train – compared with, say, on routes with more competition. A wide variety of locomotives was in use – the Patrick Stirling 4-2-2 "8-foot" singles, complemented with his 2-2-2 "7-foot 6" singles, were outstanding for speed and reliability, being capable of on flat terrain. The latest express NER engines were Tennant 2-4-0s and the T.W. Worsdell–von Borries compound Worsdell 'F' 4-4-0s which were powerful, although not so fast.
Having compound engines required the development of sufficiently strong steel connecting rods for fast running and the 4-4-0s developed from 2-4-0s when it was found that a front bogie gave greater high speed stability. The East Coast route had no severe gradients and was slightly shorter than the west.