The CRY&P had been built to haul mineral resources and agricultural products over the mountains in Sonora. For this task, they ordered 30 2-6-0 locomotives which had been derived from the Harriman Common Standard design. The first 15 were built in 1908 by ALCO-Brooks and numbered 500 to 514. Although they were operated with saturated steam, they had piston valves. The second half of the order was built by Baldwin in 1909. Their owner was now owned by the Ferrocarril de Sud Pacifico de México, a subsidiary of the Southern Pacific from the US. They were numbered 515 to 529 and had a larger grate to burn local low-calorie lignite.

In 1912 a part of the class came to other Southern Pacific subsidiaries. The locomotives of the ALCO batch became SP class M-9 and the Baldwin locomotives became class M-11. The Houston & Texas Central received seven M-9 and numbered them 550 to 556. They also received five M-11 and numbered them 560 to 564 and 576. Three M-9 came to the Arizona Eastern and became numbers 567 to 569, while their six M-11 got the numbers 570 to 574 and 576. Some years later, many got a superheater. They were retired between 1949 and 1957.