The Southern Railway and its subsidiary Alabama Great Southern operated three 2-6-8-0 Mallet locomotives which were of the same basic design as the Great Northern class L-3. Here the drivers were one inch taller with 56 inches, but the cylinders also had diameters of 23 and 35 inches with a stroke of 32 inches. A major difference was that the GN locomotives had Belpaire fireboxes, while the design ordered by the Southern used a round-topped one. In place of the traditional superheater, the exhaust from the high pressure cylinders was reheated in the smokebox. Their requirements included that they had to reach eight to ten mph with a 2,000 ton train on a grade of one percent.

The first one was built by Baldwin for the Alabama Great Southern in 1909, the same year when the Great Northern introduced its larger class. It carried the works number 33867 and became AGS class J No. 300. The Southern itself got two in 1911 which became class Ls. They carried the works numbers 36031 and 36032 and were numbered 4002 and 4003 by the Southern. The AGS already sold its locomotives in 1914 to the Chicago, New Orleans & Texas. They also operated it only for three years and so it joined 4002 and 4003 in the Southern Railway in 1917. All three were scrapped in 1935.