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Seward Viaduct

Seward Railroad Overpass Bridge

Seward Viaduct

Primary Photographer(s): Nathan Holth and Rick McOmber

Bridge Documented: August 1, 2007

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Facility Carried / Feature Intersected
PA-56 and PA-711 Over Railroad (Norfolk Southern)
Seward: Westmoreland County, Pennsylvania: United States
Structure Type
Metal 8 Panel Rivet-Connected Polygonal Warren (No Verticals) Pony Truss, Fixed and Approach Spans: Metal Stringer (Multi-Beam), Fixed
Construction Date and Builder / Engineer
1930 By Builder/Contractor: American Bridge Company of New York, New York
Rehabilitation Date
Not Available or Not Applicable
Main Span Length
109.0 Feet (33.2 Meters)
Structure Length
417.0 Feet (127.1 Meters)
Roadway Width
24 Feet (7.32 Meters)
1 Main Span(s) and 6 Approach Span(s)
Inventory Number

Historic Significance Rating (HSR)
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Bridge Documentation

This bridge no longer exists!

View Archived National Bridge Inventory Report - Has Additional Details and Evaluation

It often seems like Pennsylvania has more through trusses than pony trusses, due to all the large rivers. This bridge crosses a railroad line and is in fact a pony truss, and as such is a quality representation of a 1930s pony truss in Pennsylvania. The deck and railings have been altered, particularly on the approach, but the trusses retain integrity.

Information and Findings From Pennsylvania's Historic Bridge Inventory

Discussion of Bridge

The skewed, 417'-long bridge consists of a 106' long riveted Warren pony truss with a polygonal upper chord span and 7 rolled stringer approach spans (2 @ 35.6', 1 @ 49', 1 @ 51.9', 1@ 52.11', and 1 @ 54.11'); 6 to the west of the truss span and 1 to the east. The trusses are traditionally composed with built up members. The substructure consists of concrete abutments and concrete column and cap beam bents. The safety shape barriers date to ca. 1985. The bridge is an example of common technologies and is not technologically significant, but it appears to be significant in association with the Pennsylvania RR main line. The bridge was designed and built by the railroad on the eve of its long period of decline.

Discussion of Surrounding Area

The bridge carries a 2 lane road with one sidewalk over the former PRR main line railroad and a borough road near the intersection of SR 56 and 711 near the borough of Seward. Two other railroad tracks have been removed. PHMC has determined the PRR main line from the New Jersey to the Ohio state lines an eligible resource, but no period of significance or rating of evaluation of contributing and noncontributing resources was done as part of the determination. The bridge is outside of Seward and is not part of a potential historic district.

Bridge Considered Historic By Survey: Yes, By Association With Railroad


Photo Galleries and Videos: Seward Viaduct


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Maps and Links: Seward Viaduct

This historic bridge has been demolished. This map is shown for reference purposes only.

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2021 National Bridge Inventory: View listed bridges within 0.5 miles (0.8 kilometers) of this bridge.

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