Mainline steam trains in Great Britain
The most famous steam locomotive operating on the British main line is the 1923 built "Flying Scotsman". After being taken into public ownership in 2004, following a decade long refit it returned to mainline service in 2016. The fastest steam locomotive ever built, the 1938 built "Mallard", was also certified for main line operation briefly in the 1980s.
Tom Thumb (locomotive)
Tom Thumb was the first American-built steam locomotive to operate on a common-carrier railroad. It was designed and constructed by Peter Cooper in 1830 to convince owners of the newly formed Baltimore and Ohio Railroad (B&O)(now CSX) to use steam engines; it was not intended to enter revenue service. It is especially remembered as a participant in an impromptu race with a horse-drawn car, which the horse won after "Tom Thumb" suffered a mechanical failure. However, the demonstration was successful, and the railroad committed to the use of steam locomotion and held trials in the following year for a working engine.