The Wilmington Rail Viaduct is a series of fills and bridges, about long, that carries the Northeast Corridor through the city of Wilmington, Delaware, above street level. Constructed between 1902 and 1908, the structure consists principally of fills supported by heavy stone retaining walls, punctuated with plate girder bridges over streets, and augmented by a few sections of brick arch viaduct. Its construction is typical of the Pennsylvania Railroad's architectural practices at the time, and the viaduct has been documented by the Historic American Engineering Record and listed on the National Register of Historic Places. Built by the Pennsylvania Railroad (PRR) as part of a series of grade crossing eliminations along the Northeast Corridor, the elevation of the rail line necessitated several other changes to rail infrastructure in Wilmington, including the construction of the Wilmington Shops at the east end of the viaduct, and the construction of the Wilmington Station and adjacent Pennsylvania Railroad Office Building along the elevated right-of-way.
Physical description
The viaduct extends from Vandever Avenue, on its east end (a location on the railroad known as LANDLITH interlocking), across the Brandywine Creek and then roughly parallel to the Christina River through Wilmington Station. The west end of the viaduct is adjacent to the Alban Park neighborhood of Wilmington, an area also known as West Yard.
The bulk of the viaduct, from Vandever Avenue to Lower Linden Street, consists of earthen fill (derived from the construction excavation for the viaduct) held between heavy ashlar sandstone retaining walls resting on concrete foundations. Some of the northern sections of the viaduct have fill enclosed in timber cribbing on one side of the right-of-way, but generally the fill is contained with retaining walls on both sides. The ashlar also forms the abutments for the overpasses carrying the railroad tracks across city streets, which are steel plate through girder or deck girder bridges. The fill carries three tracks for much of its length; sidings, some now abandoned, descend to street level by ramps at various points. It was topped with of ballast before tracks were laid.
The west end of the viaduct, below Lower Linden Street, was constructed as an arched viaduct when the underlying soil was found to be too soft to support the fill carrying the remainder of the line. Originally designed in stone, shortages of sandstone led to the construction of the arches in brick, instead. Twelve arches carry the line from Lower Linden Street to the (stone) Beech Street underpass, and twenty arches continue southwest from Beech Street to the former Baltimore and Ohio and Wilmington and Northern underpass. The remainder of the structure to its West Yard end is again of retaining wall and fill construction.
The bridge over the Brandywine Creek near the east end of the viaduct had to be replaced to accommodate the newly elevated track level. At the time, this part of the Brandywine was considered navigable water, though rarely used, and the railroad had to construct a moveable bridge to accommodate navigation. The railroad chose to use a swing bridge, and began construction of the center pivot pier in the winter of 1903. The first caisson sunk there was damaged by ice and swept away in a flood. A new caisson was built resumed after the winter passed and a stone-faced concrete pier, in diameter, successfully constructed. A second pier was built in the stream to the southwest, leaving two channels between the pivot pier and the bank and the pivot and second piers. Icebreakers were built on either side of the pivot pier. (The tidal nature of the Brandywine required both sides of the bridge to be protected from ice.)
The superstructure of the bridge was manufactured by the Phoenix Bridge Company. It consists of a plate girder from the southwest bank to a fixed pier, and a fishbelly girder from that pier to the northeast bank, turning on the pivot pier. It carries three tracks. Two buildings were erected on the bridge, one for a watchman and the signal levers that protected and operated the bridge, and one to house the gasoline engine that turned it. The interlocking levers on the swing bridge were placed in service on March 4, 1906; this was the first electro-mechanical interlocking using small levers (rather than the rod-linked armstrong levers typical at the time) on the Pennsylvania Railroad system.