The 1937 AAR Box Car is widely recognized as the first standard freight car design to be voluntarily adopted by the majority of railroads throughout the United States. Although previous USRA designs also achieved widespread distribution, their success was mostly due to government control rather than popular acceptance.

The 1937 AAR Box Car also had many features that became standard on boxcars for years to come, including dreadnaught ends, straight panel roof and an inside length of 40’ 6”. They had an interior height of 10’ with a 3700 cubic foot capacity. With only a few variations built, this design helped the industry realize the economic advantages of freight equipment standardization; a concept that continues into the modern era.