The Erie was the American railroad that ordered the greatest number of 2-8-4 “Berkshire” locomotives. These 105 locomotives were not only delivered by all three major manufacturers, but also had the biggest heating surface of all Berkshires. As usual for the late twenties, they were fitted with thermic syphons, arch tubes, Worthington feedwater heaters and had a limited cutoff.
25 of the class S-1 were built in 1927 by ALCO, followed by another 25 S-2 in the same year by Lima. 35 S-3 were built by Baldwin in 1928 and 20 S-4 again by Lima in 1929. Both Lima subclasses were designed for a boiler pressure of 250 psi, but operated at only 225 psi like their sisters. These classes made it possible for the Erie to greatly accelerate their freight services and they were all scrapped between 1950 and 1952. 