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.
American Locomotive Company
Alco was the second-largest steam locomotive builder in the United States (after Lima Locomotive Works), producing over 75,000 locomotives (though not all were steam, since, unlike Baldwin, Alco transitioned more readily to Diesel). Among these were a large number of well-known locomotives. Railroads that favored Alco products included the Delaware & Hudson Railway, the New York, New Haven & Hartford Railroad, the New York Central Railroad, the Union Pacific Railroad and the Milwaukee Road. Alco was known for its steam locomotives of which the 4-6-4 Hudson, 4-8-2 Mohawk and the 4-8-4 Niagara built for the New York Central and the 4-8-4 FEF and the 4-6-6-4 (Challenger) built for the Union Pacific were fine examples. Alco built many of the biggest locomotives ever constructed, including Union Pacific's "Big Boy" (4-8-8-4). Alco also built the fastest American locomotives, the Class A Atlantic and Class F7 Hudson streamliners for the Milwaukee Road's "Twin Cities Hiawatha" run. Among the ambitious state-of-the-art designs of the late steam era, Alco's Challengers, Big Boys and high speed streamliners stood out for their in-service success.