The lightest of the USRA standard locomotives was a light switcher by US standards with three coupled axles and no carrying axles. With an axle load of 55.000 pounds, it still reached a weight that was to be found at the same time on ten-coupled freight locomotives in Central Europe. Like all USRA types, it was operated with superheated steam and, thanks to a driving wheel diameter of 51 inches and correspondingly large cylinders, achieved a starting tractive effort of almost 40,000 pounds or 175 kN.

A total of 255 examples of the actual USRA design were manufactured by ALCO in 1918 and 1919. Most customers procured between five and ten engines. The three largest operators were the Baltimore & Ohio with 40 Class D-30s, the Chicago & North Western with 35 Class M-3s and the Pennsylvania Railroad with 30 Class B28s. Later, some railroads made more pieces of the original USRA design. The Wheeling & Lake Erie only procured vehicles, of which two still exist today. While number 3984 is already being restored, number 3960 is still awaiting the start of its restoration.