The Pennsylvania Railroad's Class C1 was the heaviest 0-8-0 locomotive ever built. It had a service mass of 278,000 pounds and a maximum axle load of 74,000 pounds on the first axle. Due to its long wheelbase of 15 ft 9 in, however, the tracks were damaged and there were also frequent derailments. As far as possible, only switching locomotives with a 0-6-0 wheel arrangement were used. Nevertheless, the C1 was able to demonstrate its high tractive power on humps. The 90 locomotives were retired between 1948 and 1953. 