The last 4-4-0 locomotives the PRR procured was the class L, which was soon renamed D16. It was derived from the class P or D14, but had a higher mounted boiler with a larger Belpaire firebox. The D16 with 68-inch wheels and the D16a with 80-inch wheels were developed for different types of lines. Together with the D16c and D16d, which also had the large wheels, 429 units were built by 1910.

Since they were increasingly replaced by larger locomotives shortly after the turn of the century and were used on branch lines, many of the locomotives with large wheels were subsequently given ones with a diameter of 68 inches. From 1914 a total of 241 D16b received a superheater and became the D16sb. Some D16d also became D16sd. Many of the locomotives survived into the 1930s, some into the 1940s and a few were the last to be retired in 1953. Today only the D16sb No. 1223 still exists not operational in the Railroad Museum of Pennsylvania.