Pennsylvania Railroad 5550

Pennsylvania Railroad 5550, named Dave Fink, is a mainline duplex-drive steam locomotive under construction in the United States by the nonprofit Pennsylvania Railroad T1 Steam Locomotive Trust, which was founded in 2013. When finished, with completion estimated for 2030, it will be the 53rd member of the Pennsylvania Railroad T1 class and the only operational locomotive of its type, as well as the largest steam locomotive built in the United States since 1952. The last production T1 was number 5549, which is why 5550 was the logical number for the new engine. The T1 class had an unusual 4-4-4-4 duplex wheel arrangement, Franklin Type A oscillating-cam poppet valves and streamlining by industrial designer Raymond Loewy, and the original engines were retired between 1952 and 1953. Construction began in 2014 with the casting of the keystone-shaped number plate, and by May 2026 the locomotive was 65.4 percent complete, with all eight driving wheels, the boiler, cab, frame and cylinders finished. The builders hope to test the class against the world steam speed record held by LNER A4 Mallard.