The Light Mountain was planned as a light standard freight locomotive and had a boiler slightly larger than that of the Heavy Pacific or the Heavy Mikado. It was almost 20,000 pounds lighter than the Heavy Mountain, had cylinders that were an inch smaller in diameter, and the same driver diameter. A total of 47 were built, with the Southern Railway getting the most at 25. The rest went to the Missouri Pacific, the Nashville, Chattanooga & St. Louis, and the New Haven. By 1930, 90 more copies were built.