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Lock One Park Bridge

Blackhoof Street Bridge

Lock One Park Bridge

Primary Photographer(s): Nathan Holth and Rick McOmber

Bridge Documented: June 8, 2014

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Facility Carried / Feature Intersected
Pedestrian Walkway Over Miami and Erie Canal
New Bremen: Auglaize County, Ohio: United States
Construction Date and Builder / Engineer
1864 By Builder/Contractor: David H. Morrison (Columbia Bridge Works of Dayton, Ohio)
Rehabilitation Date
Main Span Length
57.0 Feet (17.4 Meters)
Structure Length
58.3 Feet (17.8 Meters)
Roadway Width
7.5 Feet (2.29 Meters)
1 Main Span(s)
Inventory Number

Historic Significance Rating (HSR)
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Bridge Documentation

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

View Historic American Engineering Record (HAER) Documentation For This Bridge

HAER Drawings, PDF - HAER Data Pages, PDF

This bridge, as a bridge whose compression members (top chord and verticals) are composed of cast iron (cast iron was rarely or never used for tension), is among the rarest bridges in the United States. Its rare bowstring design adds to its significance. As a pre-1870 bridge it is also among the oldest metal bridges surviving in the United States. It is the oldest bowstring truss in Ohio. It is the only cast iron bowstring truss surviving that was built by David H. Morrison.

The bridge was relocated here (the second time in its life it has been moved) and preserved for pedestrian use. It was narrowed considerably at this time.

The bridge is also significant in documenting one of the most unusual bridge companies in the country, the Columbia Bridge Works of Dayton, Ohio, which when this bridge was built didn't even go by that name yet, and was simply a small company run by the founder of the Columbia Bridge Works, David H. Morrison. David H. Morrison's company which later became the Columbia Bridge Works was noted for defiantly avoiding the period trends in terms of bridge details. Its bridges almost always have very unusual details, and oddly, their bridges tend to have a somewhat modern look to them. This is partly because the company seems to have preferred simpler truss members: for example, where other bridge companies used built-up beams with v-lacing and lattice; Columbia Bridge Works might have used rolled beams.

Even this early cast iron bowstring by Morrison has a strikingly modern appearance. Its top chord, although composed of cast iron, is a solid, simple, and unornamented member that could be compared visually to a modern welded beam. The cast iron verticals, with the oval cutouts, are almost like a foretelling of the hand-holes and cutouts that started being used in beams decades later starting in the 1940s and becoming popular in the 1950s and 1960s.

The HAER documentation describes this bridge in greater detail.

Morrison later patented a wrought iron bowstring; one example of this second generation Morrison bowstring design remains in Ohio as the Mallaham Bridge.

Information and Findings From Ohio's Historic Bridge Inventory


The bridge carries a pedestrian walk over the Miami-Erie Canal in a park in New Bremen.

Physical Description

The 1-span bowstring truss bridge has cast-iron compression members and wrought-iron tension members.

Summary of Significance

The 1864 bowstring pony truss was built by David H. Morrison, one of Ohio's most significant metal-truss bridge builders and fabricators. It's an exceptionally significant bridge, being the earliest extant example of the bowstring type/design in Ohio. It also makes use of cast-iron compression members, including the segmented arch and verticals. It was originally located at Blackhoof Street over the Auglaize River and moved to its present location in 1984. Although relocated, the truss lines maintain integrity of original design and materials. Bowstring trusses are characterized by arched top chords and a trussed or lattice web. They rank among the rarest and most technologically significant of 19th-century metal truss designs since they appeared early in the evolution of iron bridge development and were almost always based on the patents or proprietary designs of bridge builders and engineers. The progenitor of the form was the famed engineer Squire Whipple of New York, who built the first example in 1840 over the Erie Canal at Utica. After the Civil War, Ohio was a center for the development of the bowstring with its concentration of metal bridge-building companies. Companies such Wrought Iron Bridge, Champion Bridge, Massillon Bridge, and King Iron Bridge built their reputations on successful bowstring designs with a dizzying number of variant ways of forming and connecting the truss members. The companies emerged in time to fill the burgeoning demand for an economical, prefabricated bridge for use on American roads. Bowstring trusses thus document this exceptionally inventive and technologically significant period in the development of American metal trusses from the 1860s to early 1880s. The ODOT inventory has identified 22 surviving examples dating from ca. 1864 to 1880 (Phase 1A, 2008).


The bridge is one of the 22 extant bowstring truss bridges that survive in the state. Having so many is remarkable, and even though they are "common" based on their numbers, each is an important and irreplaceable record of the development of the metal truss bridge and the ingenuity associated with the Ohio industrial development. The bridge has high significance.

Bridge Considered Historic By Survey: Yes


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