In 1911, ALCO-Richmond built 24 2-6-6-2 Mallets for the Chesapeake & Ohio which were designated class H-2. They had 56-inch drivers and were able to reach speeds of 45 mph. The firebox had a grate of 72.2 square feet and a long combustion chamber. Compared to the previous Consolidations, they hauled trains which were 75 percent heavier at the same average speed, but consumed only a bit more coal. A single, virtually identical locomotive had been built in 1910 for the Chicago & Alton. This was sold to the C&O after a short time and became class H-1. Actually it can be seen as the prototype for the H-2.

Between 1912 and 1918, Richmond and Schenectady built 150 more of a slightly modified design which were designated class H-4. 25 nearly identical locomotives which had been built for the Hocking Valley Railway in 1917 and 1918 became class H-3. In 1927, H-4 No. 1470 was simpled and became the only member of sub class H-4a. It now had a much larger superheater and an Elesco feed water heater, while the boiler pressure had been increased by 10 psi. It was the only one that was rebuilt in this way and was retired in 1947. The last H-4 was retired in 1955.