At the onset of World War II, the Pennsylvania Railroad owned 581 engines of class L-1s numbered randomly from 2 to 8636. No. 533, shown in this view by an unidentified photographer, came originally from the Baldwin Locomotive Works in 1916. Like most PRR steam power, she underwent many modifications over the years as a result of the railroad's locomotive standardization program. The L-1s class had 27x30-inch cylinders, 62-inch drivers and 205 p.s.i. of boiler pressure. They weighed 320,700 pounds and exerted 61,465 pounds of tractive effort. The "s" tacked onto a PRR classification indicated the locomotive was equipped with a superheater; the L-1 class had 943 square feet of superheating surface and an evaporative heating surface of 4041 square feet. As an example of the PRR's attempt to standardize steam locomotive design, these 2-8-2s used the same boiler as the famous K-4 Pacifics.