The Gulf, Mobile & Ohio was a 1940 merger of the Gulf, Mobile & Northern and the Mobile & Ohio, and it later (1947) absorbed the Alton Route; it was also among the first North American railroads to dieselize. Consequently, images of steam power lettered for the GM&O are rare. The locomotive shown here was one of three 4-8-2s of the New Orleans Great Northern, erected in 1927 by American Locomotive Company's Richmond works. On the NOGN it bore the number 202 until 1933, when that railroad was leased by the Gulf, Mobile & Northern which renumbered it to 502. It kept the same number on the GM&O until 1947, when all three of these small, low-drivered 4-8-2s were sold to the Georgia & Florida and this engine became No. 602.

These three Mountain types, weighing 272,500 pounds, are said to have been the second lightest of any 4-8-2s erected for a North American railroad. They exerted 48,960 pounds of tractive force, having a boiler pressure of 225 p.s.i. and cylinder dimensions of 24x28 inches. Their driver diameter was 63 inches, and like other low-drivered 4-8-2s their main rod was connected to the third driving axle instead of the second. Their grate area totaled 60 square feet, their evaporative heating surface 2832 square feet, and their superheater surface 600 square feet. Although untypical for their wheel arrangement, these three locomotives survived through four railroad ownerships until being retired and scrapped in 1950. This photo of No. 502, acquired through eBay, was snapped in Jackson, Mississippi in October 1940; it came from the Harold Vollrath collection, but whether or not he was the photographer is unknown.