In North Carolina, the Southern Railway operated the famous Saluda Grade with an incline that had an average of more than four percent for several miles. For use both as main locomotive and as helper on this grade and on the Old Fort Loops, the Southern turned to the 2-10-2 wheel arrangement in World War I. So they ordered 55 class Ss locomotives from Baldwin, which were delivered in 1917 and 1918 and were numbered 5000 to 5054. In general layout, these were equipped with 57 inch drivers, cylinders of 28 by 32 inches and a duplex stoker.

But for use on those heavy grades, they got some special equipment. This included taller water gauges to provide a better readout when the boiler was inclined and a second air pump to account for the heavy brake usage. Additionally, water pipes were provided which could be used to cool down the tires of the drivers. For banking passenger trains, they even got the required cab signals.

To further increase the tractive effort of its helper locomotives, the Southern also made trials with an additional engine under the tender, also called “duplex tenders”. Concerning class Ss, at least No. 5046 also got this arrangement. Here the four-axle tender was swapped for a new one with a 2-6-2 wheel arrangement. It produced additional tractive effort of 18,000 pounds and could be engaged at low speeds when the boiler produced enough steam for both engines.

In 1918, the Southern's subsidiary Cincinnati, New Orleans & Texas Pacific ordered 25 of the same locomotives from ALCO-Richmond. Since they were too slow for the flat lines they were intended, they were also transferred to the steepest grades. Later all 80 locomotives were operated at 200 instead of 190 psi. They lasted until the end of steam and were scrapped without an exception in 1951 and 1952.