The five locomotives of class P-13A were originally the Chicago & Alton's class I-4, Nos. 605-609, delivered by Baldwin in 1908. They exerted 34,600 pounds of tractive force and had 73-inch drivers, lowest of any Pacific types on the Alton Route. But they had the 23x38-inch cylinders and 200-pound boiler pressure common to the majority of the Alton's 4-6-2s. This broadside view of No. 5272, by an unknown photographer at an undetermined location, comes from Gary Thompson. By 1947 this engine had been dropped from the Alton roster.