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Thomson Road Bridge

Thomson Road Bridge

Primary Photographer(s): Nathan Holth

Bridge Documented: April 1, 2006 and March 31, 2013

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Key Facts

Facility Carried / Feature Intersected
Thomson Road Over Railroad (Abandoned Yard)
Rural: Cass County, Michigan: United States
Structure Type
Concrete T-Beam, Fixed
Construction Date and Builder / Engineer
1919 By Builder/Contractor: Unknown

Technical Facts

Rehabilitation Date
Not Available or Not Applicable
Main Span Length
35 Feet (10.6 Meters)
Structure Length
169 Feet (51.5 Meters)
Roadway Width
20 Feet (6.1 Meters)
5 Main Span(s)
NBI Number

Historic Significance Rating (HSR)
View Information About HSR Ratings

Bridge Documentation

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

Sometimes Thomson Road shows up on maps as Thompson Road.

Some people unfamiliar with their history may wonder what this bridge is going over, and why an open field is present all of a sudden here also. MDOT provides a good historic overview of this area, but in short, there used to be a rail-yard here known as "the hump", which is long gone. The bridge remains today as a memory of this past. The bridge itself is both old and significant. The bridge was built in 1919, and is a very early example of t-beam construction. MDOT mentions that it is also unusual because it did not follow the state standard t-beam plan that was available at the time.

This bridge is also noteworthy for an attractive brick deck. Brick decks are surprisingly rare, and very few examples remain today. This bridge retains pole guardrails also. The structure is slightly skewed, which adds to the technological value of the bridge. As a five-span bridge, it is also of significant length.

This is one of the few remaining historic bridges of any kind in Cass County. Despite the fact that it no longer crosses anything, this bridge is worthy of preservation, both as an unusual structure, and a memorial to busier railroading times in this area. The bridge is currently in decent condition, with a 66% sufficiency rating in 2004 in the National Bridge Inventory, which is very high for a bridge of this age, even on a rural road.

Information and Findings From Michigan Historic Bridge Inventory

Narrative Description

The Thompson Road Bridge is eligible for the National Register as an excellent example of an early concrete T-beam bridge with very good historical integrity. This grade separation is among the oldest examples of a concrete T-beam highway bridge in the state.

The design is quite different from the standard T-beam plan which the Michigan State Highway Department had developed in the 1913-1914 biennium, but used sparingly during that decade. The plans for the Thompson Road Bridge were probably developed by the railroad company, which had a switching yard and many associated tracks in the area. The tracks under the bridge were originally operated by the Michigan Central Railroad; later, other companies assumed control over the trackage. The main line of the Michigan Central, which was built in Cass County in 1848, is about one-half mile west of the bridge site.

After the Civil War, a new railroad called the "Air Line" linked Jackson with the Michigan Central line at Niles. Within two years, the Michigan Central controlled the Air Line routes. A 1935 county history notes that a cut-off was built to connect the Air Line route and the main line of the Michigan Central in Howard Township "some fifteen years ago." That date seems to correspond to the 1919 date of the bridge. The wide right-of-way near the bridge was used as a railroad switchyard known as the "Hump."

This bridge is tagged with the following special condition(s): Unorganized Photos


Photo Galleries and Videos: Thomson Road Bridge

View Photo Gallery
2006 Bridge Photo-Documentation
A collection of overview and detail photos. This photo gallery contains a combination of Original Size photos and Mobile Optimized photos in a touch-friendly popup viewer. Alternatively, Browse Without Using Viewer
View Photo Gallery
2013 Additional Unorganized Photos
Original / Full Size Photos
A supplemental collection of photos that are from additional visit(s) to the bridge and have not been organized or captioned. This gallery offers photos in the highest available resolution and file size in a touch-friendly popup viewer. Alternatively, Browse Without Using Viewer
View Photo Gallery
2013 Additional Unorganized Photos
Mobile Optimized Photos
A supplemental collection of photos that are from additional visit(s) to the bridge and have not been organized or captioned. This gallery features data-friendly, fast-loading photos in a touch-friendly popup viewer. Alternatively, Browse Without Using Viewer


Maps and Links: Thomson Road Bridge

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