The articulated wheel-base steam locomotive represents the final phase of steam locomotive development in size and power. The cab-in-front feature was widely used by the Southern Pacific Railroad beginning in 1909 to alleviate smoke and heat problems for locomotive personnel en route through tunnels and snow sheds. This locomotive, built by the Baldwin Locomotive Works, operated between 1944 and 1956 before being displaced by a diesel-electric locomotive.
The 4,620-horsepower GG1 was primarily a passenger locomotive, routinely operating at over 100 miles per hour, but was used in freight service as well. Conceived by the Pennsylvania Railroad and built by the Baldwin Locomotive Works and General Electric Company, No. 4800 logged nearly 5 million miles in its forty-five-year life. It was the prototype for a 139-unit fleet built during a decade to serve on the PRR's electrified lines, and the only one with a riveted body shell; the remainder were welded.