A surge in World War II traffic prompted the Rock Island to augment its fleet of 4-8-4s with an order for ten oil-burning class R-67B Northerns that the American Locomotive Company delivered in 1944. Due to wartime restrictions on new steam locomotive designs their specifications were similar to those of the Delaware & Hudson's K-62 class ALCo was building at the same time. These CRI&P 4-8-4s had cylinder dimensions of 26x32 inches, a boiler pressure of 270 p.s.i., a driver diameter of 74 inches, and roller bearings on all axles. For other dimensions consult the commentary for No. 5114 following.