The article is the ninth in a series covering American box car designs that were built during the first half of the 20th century. It describes the 40’, 50-ton box and auto cars assembled or purchased by the Pennsylvania railroad that followed the design of the A.R.A. proposed-standard, all-steel box car of 1923. There were more than 29,000 of the X29 prototype cars built from 1924 to 1934, which included a large fleet of BX express box cars.
The article is the tenth in a series covering American box car designs that were built during the first half of the 20th century. Described are the box and automobile cars that were built new as U.S.R.A. double-sheathed, wood-sided 40-ton box cars immediately after World War I and rebuilt as improved all-steel cars beginning in the 1930s. The owners/operators of the rebuilt steel-sided box and auto cars included the ACL, ATSF, C&WC, C&NW, CMO, CRI&P, DL&W, DT&I, EJ&E, GTW, KCS, NYC, and SL-SF (a total of 9,962 cars).