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. The Railroad Age Gazette for October 2, 1908, included an article on the construction of the I-4 class which will open as a PDF in a new window.