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Tilton Island Park Bridge

Tilton Island Park Bridge

Primary Photographer(s): Nathan Holth

Bridge Documented: June 16, 2012

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Key Facts

Facility Carried / Feature Intersected
Pedestrian Walkway Over Winnepesaukee River
Tilton: Merrimack County, New Hampshire and Belknap County, New Hampshire: United States
Structure Type
Metal Truesdell Pony Truss, Fixed
Construction Date and Builder / Engineer
1881 By Builder/Contractor: A. D. Briggs of Springfield, Massachusetts

Technical Facts

Rehabilitation Date
Not Available or Not Applicable
Main Span Length
Not Available
Structure Length
83 Feet (25.3 Meters)
Roadway Width
10 Feet (3.05 Meters)
2 Main Span(s)
NBI Number
Not Applicable

Historic Significance Rating (HSR)

Bridge Documentation

View the National Register of Historic Places Nomination Form For This Historic Bridge

View the Original Patent For This Bridge's Truss Configuration

This bridge, constructed in 1881 with cast iron compression members, is a very late example of a truss bridge with cast iron compression members. Cast iron was used in bridge construction in the United States mostly from the 1840s through the early 1870s. It quickly gave way to wrought iron, which already was usually used for tension members, since brittle cast iron breaks under tension. Despite being a late example, this bridge is nationally significant as one of the few remaining examples of cast iron bridges in the United States. Additionally, like many cast iron bridges, it displays unique patented design details. In this case, the unique detail is the truss configuration, the only known surviving example of its type. The truss configuration was patented by Lucius E. Truesdell in 1859. Apparently, some examples of a span length longer than the Tilton bridge were built soon after in the Midwest, but soon collapsed under heavy loads, demonstrating that the Truesdell truss was destined to become one of many mid-1800s experiments in bridge design that quickly faded into memory. However, the Tilton Bridge was an exception. Albert D. Briggs, who had been an agent for Truesdell truss bridges, was able to attract the interest of Charles Tilton, who was the grandson of the founder of Tilton, and was using his wealth to create a park on this island. In 1881, Briggs constructed a Truesdell truss that has stood the test of time and remains today in good condition. The short spans seen in this bridge appear to make up for the shortcomings in the truss configuration that led to collapse in the earlier examples. The bridge was likely erected on-site by J. R. Smith of Springfield, Massachusetts.

Be sure to view the National Register Nomination link at the top of this narrative. The extensive nomination documentation provides a detailed history of the bridge.


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