Originally made of all wood construction, with beam frame, and frame sides and roofs, the cars were a fire hazard. The beam frame was limited to a length. In the 1930s, pressed steel ends were added as were steel under framing. In the late 1960s the Federal Railway Administration outlawed wood cars and they were slowly removed from the fleet. With steel frames, longer box cars were possible and thus cars emerged. Heavy loads of cement or beer can make a boxcar load in the range.