The class C-43 of the Rock Island didn't technically designate a series of similar locomotives, but only stood for Consolidations with a tractive effort of around 43,000 pounds. 83 locomotives with the numbers 1701 to 1783 were built by Baldwin in 1906. With drivers of 63 inches and cylinders of 23 by 30 inches, they initially only produced a tractive effort of 39,600 pounds. Only after they got larger cylinders when being superheated starting in 1918, they produced 43,100 pounds. ALCO-Brooks built numbers 1901 to 1930 in 1907 which were similar to the first batch.

Also in 1907, ALCO-Schenectady built numbers 2100 to 2144 which had drivers of only 57 inches and a higher boiler pressure and produced 43,300 pounds even with cylinders of only 22 by 30 inches. They had a firebox that was somewhat larger than that of the earlier Consolidations, but with roughly the same grate area. Most were later superheated and were fitted with thermic syphons which increased the grate area from 183 to 240 square feet. Like the earlier Consolidations, they were retired between 1936 and 1953.