In 1926, ALCO-Richmond built six Mikados for the Monon which were based on the USRA Light Mikado. But compared to this, the boiler and the cylinders got bigger, while the driver diameter was still 63 inches. They were numbered 560 to 565 and formed the class J-3. Three years later, ALCO-Schenectady built ten similar locomotives which were numbered 570 to 579 and formed the class J-4. These were among the last new steam locomotives built for this railroad. Later the J-4 was rebuilt with a trailing-truck booster and a larger boiler with thermic syphons and a feed water heater. Five also got roller bearings. Since the J-3 and the original J-4 were similar, the specs for the J-4 in the table are for the rebuilt variant. Both classes lived until the end of steam on the Monon. No. 578 shown in the photo was sold to the Tennessee, Alabama & Georgia in 1948 and numbered 402. It was scrapped in 1951.