In February 1917, Ralston Steel Company delivered 450 of these class SM cars to Southern Pacific. It is a 40’ despatch stock car with single door and is painted brown with white lettering. Railroads have long played a key role in livestock transportation. In the early days of perishable shipments, freshness was ensured if livestock could be delivered to market on the hoof. Stock cars were developed to meet this need. Southern Pacific, with over 11,000 miles of track, has been a major mover of livestock.