Missouri Pacific 4-6-2 No. 6001 was originally built as three-cylinder locomotive No. 6000 in 1925 by the American Locomotive Company. Due to the cost of maintaining the Walschaerts-Gresley-geared cylinder arrangement the locomotive was set aside for many years. In 1942, however, the railroad's shops in North Little Rock, Arkansas rebuilt her as oil-burner No. 6001 with the oscillating-cam poppet valves being promoted by manufacturer Franklin Railway Supply Company. As the sole member of class 6001 she weighed 306,380 pounds and developed 47,535 pounds of tractive effort. Cylinder dimensions were 27x28 inches, boiler pressure 200 p.s.i., and driver diameter 73 inches. With a grate area of 67 square feet, she had 4028 square feet of evaporative heating surface and 1354 square feet of superheating surface. Although "Madam Queen," as she was known, proved to be a fast, powerful, and reliable engine and served well until 1952, the MoPac declined to apply the same conversion to other members of its fleet of Pacifics. In this view acquired via eBay the newly-rebuilt No. 6001 poses at North Little Rock on November 16, 1942; based on similar photos encountered elsewhere, the photographer may be R. J. Foster.