Within a few years after the introduction of the 1932 ARA standard box car design, the inside height of house cars began to increase, primarily through the efforts of the Pennsylvania Railroad and its X31 family of cars. By 1937, the AAR had increased the inside height of its standard design to 10’0” (and the inside width to 9’2”.) In the intervening years, a few roads experimented with cars that were based upon the existing AAR standard design, but with slightly taller inside dimensions.

The Western Pacific received 200 of these cars from Mt. Ver-non Car Manufacturing Company in 1937. They were placed in the 20001-20200 series. They had an inside height of 9’6”. Includes two of the artwork shown.