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Insley Road Bridge

Insley Road Bridge

Primary Photographer(s): Nathan Holth

Bridge Documented: May 5, 2006

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Key Facts

Facility Carried / Feature Intersected
Insley Road (CR-604 / Dixie Highway) Over Rocky Ford
Rural: Wood County, Ohio: United States
Structure Type
Concrete Rainbow Through Arch, Fixed
Construction Date and Builder / Engineer
1930 By Builder/Contractor: Unknown

Technical Facts

Rehabilitation Date
Not Available or Not Applicable
Main Span Length
63 Feet (19.2 Meters)
Structure Length
95 Feet (28.96 Meters)
Roadway Width
28 Feet (8.53 Meters)
1 Main Span(s)
NBI Number

Historic Significance Rating (HSR)

Bridge Documentation

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

This is a beautiful example of the rainbow arch structure type. The technical name is a concrete through arch bridge. They are a very attractive bridge design, and among the most impressive and rare of concrete bridge types. This is a good example of the structure type, having retained historic integrity, with no railing or floor beam modifications.

As of 2013, this bridge has been closed to traffic and has an uncertain future. While it has been found eligible for listing in the National Register of Historic Places and has High Significance according to the Historic Bridge Inventory, Wood County is not exactly noted for preserving historic bridges, although its not to late (yet) for them to change this reputation.

The bridge does suffer from severe deterioration in certain areas including spalling and extensive map cracking with efflorescence found on the floor beams and deck. The arch, hangers and railings are all in much better condition. A possible preservation scenario would be to replace the deck and floor beams completely, while repairing the arches. 

Information and Findings From Ohio's Historic Bridge Inventory


The bridge carries a 2 lane road over a stream in a sparsely developed, rural setting.

Physical Description

The 1 span, 95'-long, rainbow (thru) arch bridge has flat-paneled arch ribs with floorbeam hangers and articulated floorbeams. Concrete balustrades fill between the hangers, and flat-panel parapets extend between the arch ribs and the wingwalls.


Some loss of fabric from spalling.

Summary of Significance

The rainbow arch bridge built in 1930 is a complete, albeit later, example of a bridge type that was in use from the late 1900s to 1930s. The inventory has identified seven surviving examples dating from 1909 to 1930 (Phase 1A Update, 2008). This one, like several others, appears to be the state bridge bureau's design that was in use during the 1920s to early 1930s based on the details.

The rainbow arch in the U.S. developed in the late 1900s and early 1910s, with its best known variation the 1912 patented design of James B. Marsh of Iowa, (which is debatably a steel arch encased in concrete). In the basic design the deck is supported by vertical hangers between the arch ribs and the floorbeams. The arch ribs, like Marsh's can have patented steel systems within them, or they can be un-patented systems of conventional reinforced concrete. The bridge type/design is known to be aesthetically pleasing and came to be popularly known as "rainbow" arches in some parts of the country, including Ohio, although technically they are perhaps best described as thru arches. The bridge type was always more numerous in the Midwest than other parts of the U.S., probably because of the influence of Marsh. The 1909 and 1911 thru arches designed by E. A. Gast in Hamilton County (3137600 & 3130622) are Ohio's oldest examples and very technologically significant as they predate the Marsh patent and are believed to have been developed independently. Later examples in Ohio are most often the design of the state bridge bureau, which developed its own standard rainbow arch by 1923.


The bridge is one of 5 remaining examples of the type that was once not uncommon in Ohio. It offered an aesthetic treatment preferred in urban and picturesque settings. The 6 examples date from 1909 to 1930, and each is of high significance given their limited numbers and importance within the context as the aesthetic alternative to the thru truss bridge.

Bridge Considered Historic By Survey: Yes


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