This bridge is a rare example of a pony truss composed of Phoenix columns. In 1948, bents were added under the bridge so today the trusses are not functional and serve a decorative purpose only. However, the structure type is so rare it does not diminish the significance of the bridge. The pony truss, like a number of other Phoenix column pony truss bridges, has outriggers that become part of the v-lacing on the vertical members. These outriggers have been altered on this bridge but maintain the original positioning where they are part of the v-lacing.
Information and Findings From New Jersey's Historic Bridge Inventory
Discussion of Bridge
The pin-connected 4-panel Pratt pony truss has Phoenix Column top chords and end posts. In 1885 the Phoenix Bridge Company fabricated the truss for erection by New York City engineers Dean and Westbrook. In 1948 the bridge was underpinned with timber piles. The masonry abutments have been repaired with concrete numerous times. The bridge no longer functions as a truss, but its technological significance and date make it a contributing element to the Walnford Historic District (c.1770-1900).
The bridge is a 4-panel, cast and wrought-iron pin-connected Pratt pony truss with Phoenix Column sections for the upper chords and inclined end posts. The two members are joined by cast pieces. The lower chords are stamped eye bars, the verticals are angles with lacing, and the diagonals are loop welded eye bars. The counters are connected to the upper panel point by a clevis rather than an eye. The bottom connection, however, is the traditional eye loop. Another unusual feature is the outriggers which are similar to those on a 1885 Dean and Westbrook Phoenix column pony truss bridge in Hunterdon County (10XXF65, Hamden Road over South Branch of the Raritan River, Franklin Twp.). The outriggers on this bridge have been reconnected by welds, so while an original detail, the way they are connected is not. The trusses bear on girders that rest on masonry abutments that have numerous concrete repairs and reinforcing. The placement of the built-up floor beams above the lower chord with bolted connections is an original detail. Braced timber pile bents with I-beam cap beams have been placed at each floor beam to underpin the trusses. Deep timber stringers bear on the bents, so the span now generally functions as a timber stringer bridge rather than a truss span. Other alterations include removal of the original railings and installation of beam guide rails. There are some minor repairs and strengthening.
Historical and Technological Significance:
The Pratt pony truss bridge is a historically noteworthy example of late-19th century iron truss bridge construction using the patented Phoenix Column section. Walnford Road is the western border of the Walnford Mill Historic District, an eighteenth and nineteenth century historic site with large dwelling house (c.1773) and grist mill (c.1871) administered by the Monmouth County Park Commission. The bridge is a contributing structure and is eligible under both Criteria A and C of the National Register for its association with the historic events surrounding Walnford Mills, and as an example of a rare surviving bridge type embodying the characteristics of a significant type, period, and method of bridge construction. It was constructed within the period of significance of the historic district, and it retains its historic appearance.
Phoenix Bridge Company records date the Walnford Mill Road bridge to 1885. The company fabricated the bridge in its shops at Phoenixville, Pennsylvania under order from New York City engineers Dean and Westbrook. From the mid-1880s to the early 1890s Dean and Westbrook held an agreement with the Phoenix Bridge Company as agents for the construction of Phoenix Column highway bridges. Dean and Westbrook took responsibility for bidding the bridges, signing contracts with local officials, providing accurate information for Phoenix engineers to prepare plans and shop orders, and erecting the bridges on site. In New Jersey from 1885 to 1895 Dean and Westbrook erected at least 71 documented Phoenix Bridge Company truss bridges, of which six are known to survive (10XXF65, Hamden Road over South Branch of Raritan River, 1885, Franklin Twp., Hunterdon Co.; 10XXF82, Lower Lansdowne Road over Capoolong Creek, 1885, Franklin Twp., Hunterdon Co.; 1300U53, Province Line Road over Crosswicks Creek, 1891, Upper Freehold Twp., Monmouth Co.; 020042A, Doty Road over Ramapo River, 1891, Oakland Borough, Bergen Co.; 020044B, Elm Street over Hackensack River, 1892, Oradell Borough, Bergen Co.).
The patented Phoenix Column was developed in 1864 by David Reeve of the Phoenix Iron Company of Phoenixville, Pennsylvania. Its significance in the history of civil engineering was as a leading contribution to the substitution of wrought iron for cast iron in the compression members of bridges and buildings. It enjoyed tremendous popularity in the 1880s, and was important in the general acceptance of metal truss bridge technology. In the late-19th century the Phoenix Bridge Company, an offshoot of the Phoenix Iron Works, was one of the nation's leading innovators in structural iron and steel construction and a training ground for numerous civil engineers. Although the Walnford Road bridge has been altered and no longer functions as a truss, it retains enough integrity of design to be considered an important example of a rare bridge type. Its significance is greatly enhanced by documentation of its construction in the Phoenix Bridge Company records. Company order books include casting and forging instructions for every bridge member, and it is possible to follow the truss fabrication from iron foundry and roll mill to machine shop. This level of documentation is rarely encountered and in combination with records that survive for other Phoenix Column trusses provides a laboratory for the study of late 19th-century bridge construction technology.
The Walnford Road bridge spans Crosswicks Creek at the Walnford Mill Historic Site. The Walnford Mill Historic District nomination lists the Walnford Road as one of the western boundaries of the district. The bridge was not rated in the nomination, but it appears to be within the district. It was built within the period of significance (c.1700-1899) of the district, and it contributes to the themes developed in the nomination. It is therefore a contributing resource.
The bridge played an important role in the transportation system that linked the mill, active until about 1929, with the surrounding country side, and it helped make the mill the economic center of the local agricultural-based economy. The historic crossing has been in use since at least the eighteenth century, and the current truss is the last of several bridges that have stood at or near the present right-of-way. The truss is an important element of the district's historic character. It is located just downstream from the grist mill, and is south of a stringer bridge with Phoenix Column piers that spans the river flood plain (1300U48).
Inspection reports and alteration plans at the Monmouth County Engineer's office indicate that in 1948 the bridge was underpinned. The timber pile cap beams were welded to the truss floor beams, new bridge seats poured, and the existing stone and concrete abutments repaired. Timber bulkheads were added. In 1969 the timber stringers and deck were reconstructed.
Boundary Description and Justification: The Walnford Road bridge is a contributing structure to the Walnford Mill Historic District. Walnford Road forms the western boundary of the district, but revisions to the nomination are currently underway to amend it to specifically rate the bridges and include newly acquired property on the east side of Walnford Road. Because the bridge is part of a larger historic setting, both it and its surroundings are evaluated as significant.
Burnham, Alan. "Forgotten Engineering: The Rise and Fall of the Phoenix Column." Architectural Record. April 1959.
Discussion of Surrounding Area
The single-lane bridge spans Crosswicks Creek in Walnford County Park, a National Register Historic District with grist mill (1871) and house (1773) to the northeast of the bridge. The picturesque historic site was the home of a prominent Quaker family. Just north of the bridge on Walnford Mill Road is a steel stringer bridge with Phoenix Column piers spanning the flood plain of Crosswicks Creek (1300U47).
Bridge Considered Historic By Survey: Yes
This bridge is tagged with the following special condition(s): Phoenix Columns
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