Despite the widespread use of steel in passenger cars after the turn of the century, the
basic shape of cars varied little from the standard wooden designs of the 1880s which always
featured the clerestory roof. The clerestory is the broad hump along the center of the roof
perforated with transom windows which helped to ventilate the car's interior. Long after cars were sealed for heating and air conditioning, most passenger cars were still manufactured with the old-fashioned clerestory roof, even though it no longer served any practical purpose in climate control.
This Southern Pacific car was one of the first all-steel, Chair Cars which abandoned the clerestory design. Cars with this effective, barrel-vault shape were called "Harriman cars," named after the
railroad mogul and once owner of the Southern Pacific Railroad, Edward Harriman. The spacious,
rounded ceiling was a refreshing exception to clerestory design.

     The interior of steel cars, however, did differ from their wooden predecessors, in one way—they were more austere. The inside walls of the cars were sheets of steel riveted onto steel frames,
and were usually painted with a smooth layer of plain, pale green. The luxury of furnished, wood walls and the fine appointments that went with them were omitted, almost as though to make passengers suffer for the presumed safety a steel car offered. A Chair Car, such as this one, was simply a car furnished with thirty or forty benches for "day long" trips. Only very late in the 1920s did some
railroads reintroduce elegant touches into passenger cars