A locomotive is a pulling vehicle for the trains used in Rail Transport. In the 19th century and in the early 20th century, locomotives were powered by steam engines. Before the middle of the 20th century, the transition to diesel-electric power was under way. By 1960 there were few steam powered locomotives in commercial service.
Well before the end of the 20th century, almost the only steam power still in regular use in the U.S. was on railroads specifically aimed at tourists and/or railfans.