Prior to the invention of this type, coils of sheet steel were carried on end or in cradles in open or covered gondolas. Load shifting, damage, and awkward loading and unloading were all problems with this type of loading, and since so much sheet steel is transported, a specialized car was designed for this use.
These cars started to appear in the 1960s. Early examples include the Pennsylvania Railroad G40 and G41 class cars, built in 1964-65.[1]