The Alton & Southern was owned by the Aluminum Company of America (ALCOA) and connected St. Louis, Missouri with East St. Louis, Illinois. Between 1925 and 1928, ALCO-Schenectady built four similar Mikados for this railroad with 55-inch drivers. All had cylinders of 25 by 30 inches and a grate area of 66.8 square feet. Numbers 10 and 11 were completed in 1925, followed by 13 in 1917 with slightly less heating surface. No 14, soon renumbered to 2, was built in 1928. It had a firebox heating surface of 296 instead of 243 square feet thanks to thermic syphons. All these locomotives were retired in 1950.