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Mill Road Bridge

Mill Road Bridge

Primary Photographer(s): Nathan Holth and Rick McOmber

Bridge Documented: August 1, 2007

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Facility Carried / Feature Intersected
Mill Road Over Conneaut Creek
Near Conneaut: Ashtabula County, Ohio: United States
Structure Type
Concrete Rainbow Through Arch, Fixed and Approach Spans: Concrete Slab, Fixed
Construction Date and Builder / Engineer
1925 By Builder/Contractor: Unknown
Rehabilitation Date
Not Available or Not Applicable
Main Span Length
150.0 Feet (45.7 Meters)
Structure Length
224.0 Feet (68.3 Meters)
Roadway Width
22.3 Feet (6.8 Meters)
1 Main Span(s) and 2 Approach 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

This bridge is a reinforced concrete through arch bridge, an uncommon bridge type often called a rainbow arch bridge. Among rainbow arch bridges, this structure is a long example, a trait that makes it both historically significant and impressive to look at. The bridge is large enough that it includes overhead bracing, which adds to the visual experience as one crosses the bridge. This bridge is visible from the new alignment of OH-7, while the historic bridge carries one-way local traffic. A trip off of OH-7 is recommended to get a better look at this large example of a rare structure type.

This bridge is one of two similar bridges in the county, the other being the Center Road Bridge, both located on old OH-7 alignment. The Center Road Bridge differs from the Mill Road Bridge in that it has been rehabilitated. It would be nice to see the Mill Road Bridge rehabilitated as well, as the Mill Road Bridge is a magnificent structure as well. The Mill Road Bridge retains original railings, but these are in poor condition and may suggest why the railings on the Center Road Bridge were replaced. The same may have to be done with the Mill Road Bridge. The abutment railings are solid panel rather than balustrade, and they appear to be in much better shape. The Mill Road Bridge features the same span size as Center Road, but features approach spans that appear to be integrated with stone abutments that may be from a previous structure, to make up the distance, resulting in a longer total structure length listed in the National Bridge Inventory.

A pre-1900 date was given for this bridge by the National Bridge Inventory, but it was likely built around 1925, since it is nearby and on the same road as the 1925 Center Road Bridge. The NBI sometimes lists the oldest possible date for any part of the bridge; since the stone abutments are apparently from a previous structure, this pre-1900 date may refer to that. Ashtabula County is just lucky to happen to have two of these extremely rare, large, and significant examples of a beautiful structure type.

Information and Findings From Ohio's Historic Bridge Inventory


The bridge carries a 2 lane road over a stream in a rural setting with scattered 20th century residences.

Physical Description

The 1 span, 154'-long, reinforced-concrete thru arch has paneled upper lateral struts and is finished with concrete balustrades. The approach spans appear to be slabs or T beams.


Rehabilitated in 1999.

Summary of Significance

The 1925 rainbow arch is a complete example of a rare bridge type/design in Ohio. It was sensitively rehabilitated in 1999. The inventory has identified seven surviving examples dating from 1909 to 1930 (Phase 1A Update, 2008). The eligible recommendation of the prior inventory remains appropriate.

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


Photo Galleries and Videos: Mill Road Bridge


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Maps and Links: Mill Road Bridge

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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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