The heaviest of the US Railroad Administration standard designs was a 2-8-8-2 Mallet. It was strongly based on the Norfolk & Western class Y-2, which had found a good solution to the biggest problem of such large locomotives. While the amount of steam produced was normally no longer sufficient at speeds above 20 mph, the Norfolk & Western used smaller cylinders and a high boiler pressure of 240 psi for the first time.

A total of 106 examples were produced from the original USRA design, of which the Norfolk & Western got the most with 45 pieces and used them as class Y-3. Five of them were actually intended for the Virginian and were not accepted. Later, the Virginian took 20 more locomotives, and more went to the Baltimore & Ohio and the Clinchfield. A total of 116 copies were later made. Customers now also included the D&RGW, the Northern Pacific and the Interstate Railroad.