#178 in the Altoona Shops, giving it a superheater for greater power and efficiency. This necessitated replacing the slide-valve equipped cylinders, the lubrication of which was incompatible with the hotter, dryer superheated steam, with piston valves and slightly larger cylinders. Steam pressure was reduced by to . Tractive effort increased to from . The rebuilt locomotive was classified D16sb, the "s" referring to superheat. The conversion proving a success, over the next few years 241 locomotives of various D16 sub-classes were converted to D16sb configuration, with 68-inch drivers. In addition, a number of high-drivered locomotives were rebuilt; these were classified D16sd. Later career Even by the early 1900s the 4-4-0 type was becoming eclipsed by larger types such as 4-4-2 "Atlantics" in top-flight service, and the D16 locomotives became stalwarts on more pedestrian services; slower trains, locals, branch line service, and commuter services. The rebuilds to D16sb and D16sd gave them a new lease of life in such service, and even by December 1929 there were still 143 examples in operation, mostly in the Eastern and Central Regions. A number were sold to the small Kishacoquillas Valley Railroad in Belleville, Pennsylvania, and the quantities in service with the PRR dwindled progressively as train lengths increased and newer locomotives trickled down, especially with the reduced traffic of Depression years and with steam locomotives made surplus by the railroad's electrification projects. Last survivors The last of the PRR's American types were found on the branch lines of the Delmarva Division, on the Delmarva Peninsula, encompassing parts of the U.S. states of Maryland, Delaware and Virginia. Three locomotives were left at the beginning of World War II, numbers 1035, 1223 and 5079; of these, only 1223 retained its slatted passenger pilot. This locomotive, a 1905 product of the Juniata Shops, was selected by the railroad for preservation as a historic artifact and was stored at Wilmington, Delaware until 1951, following which it was placed in the PRR's historic collection in the roundhouse at Northumberland, Pennsylvania. In 1953, the last of the D16s were retired. Strasburg Railroad In 1960, the 1223 was leased and transferred to the Strasburg Rail Road, a tourist line in the Amish hamlet of Strasburg, Pennsylvania, where it was returned to operating condition. It operated tourist trains there until 1989, successively leased by the PRR, its successor Penn Central from 1968, and the Railroad Museum of Pennsylvania from 1979. While