Boxcar, 40 Foot, AAR 1937

History: The Association of American Railroads had been establishing design standards for freight cars since the early part of the century. Each new design standard meant higher capacity, lighter, more durable cars.

The Modified 1937 AAR boxcar design was a result of the industries continued search for more freight volume per carload. The real first attempt at a standardized design had been the 1932 ARA steel boxcar with an inside height of 9'-4" . In 1936 the board of the AAR approved the 1937 AAR design with a 10'-0" inside height. This became a standard throughout the industry.

Railroad/Company: The Association of American Railroads (AAR) is an industry trade group representing primarily the major freight railroads of North America (Canada, Mexico and the United States). Amtrak and some regional commuter railroads are also members. Smaller freight railroads are typically represented by the American Short Line and Regional Railroad Association (ASLRRA), although some smaller railroads and railroad holding companies are also members of the AAR. The AAR also has two associate member programs, and most associate members are suppliers to the railroad industry.

Where appropriate, the AAR represents its members' interests to the public at large and to Congress and government regulators in particular. The AAR works to improve the efficiency, safety and service of the railroad industry, such as through its responsibility for the industry's interchange rules and equipment specifications, e.g. for locomotive multiple unit control. One of the AAR's duties is to oversee the assignment of reporting marks – two to four letter codes that uniquely identify the owner of any piece of railroad rolling stock or intermodal freight transport equipment (trailers, semi-trailers, containers, etc.) that can be carried on a railroad.

From Wikipedia