“At the beginning of the 20th century, all essential transport and machine movement, even in the building trade, was by water or rail. This left its marks on the cranes of the day, and a large number of rail-mounted crane structures were utilized – including the rather strange looking ‘crane locomotives’. These were steam locomotives to which a steam crane had been added.”
Quote & picture from “The History of Cranes (The Classic Construction Series)“, Oliver Bachmann (Amazon link). More pictures below.