CB&Q class S-2A Pacific No. 2945 poses at Galesburg, Illinois on June 12, 1949 for the camera of D. W. Eldridge, in an image supplied by an eBay vendor. Delivered by Baldwin in 1910 as class S-2, many of the fifty engines of this class underwent extensive rebuilding in the West Burlington shops during the 1920s (while others were instead retired in the 1930s). Among other changes, driver diameter was raised from 69 to 74 inches and boiler pressure from 160 to 200 p.s.i. .

Additional improvements, for some engines at least including No. 2945, evidently included the installation of Elesco feedwater heaters and a Delta trailing truck, although some photos of other members of this class reveal that these were not universally applied. Cylinder dimensions for the class are given as 25x28 inches, although again there was some variation in the diameter. With an evaporative heating surface of 3469 square feet and a superheater surface of 797 square feet, they had just short of 59 square feet of grate area. Locomotive weight is stated as 236,100 pounds, though due to different features the weight must have varied among these engines. Members of the S-2A class produced a tractive effort of 40,203 pounds. Per a spreadsheet issued by the Burlington Route Historical Society, No. 2945 was retired in 1953.