Louisville & Nashville J4 No. 1780
In addition to the Light Mikado, the USRA standard designs also included the heavier variant, which basically had the same running gear. However, it received larger cylinders and a significantly heavier boiler. Although similarly sized Mikados were still being built without a stoker at the time, USRA locos had one as standard. The largest customer was Milwaukee Road, which took 100 units and designated them as Class L3. By 1922, a total of 233 original USRA standard design Heavy Mikados had been built. A further 724 copies were built by 1944, based directly on the design. 