The Burlington Route called its 2-10-4s the Colorado type, instead of the usual Texas type, probably because when first introduced they were put to work in the western lines of the railroad whose slogan was "Everywhere West." This photo, scanned from the 1950 edition of Rand McNally's World Railways, probably shows No. 6311 in service in a western location pulling a train of refrigerator cars bound for eastern markets. However these engines, without doubt the Burlington's heaviest and heftiest steam power, spent their later years hauling coal drags through central and southern Illinois.
No. 6311 belonged to the first group of 2-10-4s Baldwin Locomotive Works delivered to the CB&Q in 1927; all were rebuilt as class M-4A in the late 1930s and early 1940s. As rebuilt they weighed in at 504,570 pounds and exerted 83,300 pounds of tractive effort. With 64-inch drivers, they had cylinder dimensions of 28x32 inches and carried 250 p.s.i. of boiler pressure. They had a grate area of 106.5 square feet, 5907 square feet of evaporative heating surface and 2487 square feet of superheating surface. Some were in service at least as late as the end of 1956, when I photographed No. 6316 at Galesburg, Illinois. None of these locomotives escaped the salvager's torch.