Between 1911 and 1914 the locomotives were rebuilt with superheaters and other upgrades, and were reclassified as Ps-2. Interestingly, the Ps4 class was the final batch of Pacifics the Southern owned and spanned nearly 10 years from the railroad's last order of 4-6-2s.

For instance, between 1905 and 1914 the company purchased or reclassified a total of seven different batches of Pacifics which included Class P, P-1, Ps-2, H/H1, H-1/Ps, H/H-2, and H/Ps-3. The Ps4 was not built until 1923 with most manufactured by Alco's Schenectady and Richmond plants.

These totaled 23 units (#1366-1392) and three years later in 1926 the railroad ordered 20 additional examples, which also came from Alco.