History: The 50-foot boxcar made its first appearance in the 1930s and steadily grew in popularity over the years, which further improved redundancies by allowing for even more space within a given car. Today, the 50-footer remains the common boxcar size. After the second world war ended, and steel became once again readily available, steel became the go-to choice for construction of boxcars. Pullman Standard and ACF were some of the most prolific builders of these cars.
In the 1960s, the flush, “plug” style sliding door was introduced as an option that provides a larger door to ease loading and unloading of certain commodities. The tight-fitting doors are better insulated and allow a car’s interior to be maintained at a more even temperature.