2.8.8.2 Mallet Articulated Compound Locomotive, Southern Pacific RY. Editorial Image

Steam locomotives were first developed in the United Kingdom during the early 19th century and used for railway transport until the middle of the 20th century.The Southern Pacific was an American Class I railroad network that existed from 1865 to 1996 and operated largely in the Western United States. The system was operated by various companies under the names Southern Pacific Railroad, Southern Pacific Company and Southern Pacific Transportation Company.