In the 1920s many railroads in the United States of America had retired 0-4-0 steam locomotives, because they were too small to move freight cars in yards and were too small for switching duties. This was not the case on the Pennsylvania Railroad. The Pennsylvania Railroad was keen on this wheel arrangement due to complex street and tight industrial trackage across its broad system of trackage. For some of these lines, the Pennsylvania Railroad needed a large 0-4-0 to handle the larger switching activities the railroad had. Although the class B was designated for steam locomotives with the 0-6-0 wheel arrangement, these steam locomotives could not fit the tight and complex street, dockyard and industrial trackage the Pennsylvania Railroad had in its possession.
In as early as 1956, the A5s steam locomotives started to be replaced by higher horse powered and heavy duty diesel switchers. For the next year, these switchers were gradually replaced by diesel locomotives. Finally in 1957, the Pennsylvania Railroad converted from steam to diesel power and the end of an era was finished.