4 3/4 Mile Road Bridge

Visit MDOT's Page For This Historic Bridge

This Bridge Has Been Relocated to Private Property and Restored.

As a person who grew up near Port Huron Michigan, I have a personal interest in this bridge, which is the only bridge I have found to date that was built by the Tunnel City Bridge and Iron Works of Port Huron. In case you are curious why the company named themselves "Tunnel City" I have a pretty good idea why. In 1891s, the first full-size sub-aqueous tunnel in North America was completed, running from Port Huron, MI and Sarnia, ON. In 1903 when the 4 3/4 Mile Road Bridge was built, this key international tunnel would have been a major source of fame for Port Huron. Engineers would have possibly nicknamed Port Huron "Tunnel City" back then. Click here to visit HABS HAER's page for this historic tunnel.

This bridge has been moved for a number of years, as MDOT's website mentions, and it took me some searching to find who moved the bridge and where it moved. It turns out that a nearby resident, Jim Hyatt, moved the bridge to a nearby private drive and restored it. I can not imagine how much work this was for one person to organize, but I am appreciative that this beautiful piece of Port Huron heritage was saved from the dumpster, which is where the Midland County Road Commission was going to put it.

Constructed in 1903, this bridge is a classic example of a pin connected Pratt through truss. The bridge is composed of eight panels yielding a 120 foot span. V-lacing is present on the vertical members, and lattice is present on the portal bracing. The original railings on the bridge are also lattice.

I was pleased with the restoration of this bridge. The original railings have been retained on the bridge, and the overall appearance of the bridge is excellently maintained. The only area of modification that is easy for a bridge enthusiast to note is that the bottom chord was modified, including plate steel welded on a number of parts. Steel was also welded to the bottom of the end posts. These areas of truss bridges are always troublesome spots, since rust damage in these locations is usually bad. The flooring system was also replaced, but with a wooden deck. Although MDOT's website mentions that the deck of the bridge was originally concrete, wood was a common surface for pin connected through truss bridges.

The plaque on the bridge is not original, and was made for the bridge restoration. the plaque was missing from the bridge when it was moved. I however thought the plaque was excellent, as the shape and text layout was based on what original plaques on other through truss bridges look like. Compare this to what officials put on the Sterling Road Bridge, which is not authentic, and looks inappropriate on the bridge.

I want to thank Jim Hyatt for allowing me to visit and photograph this fascinating bridge, and also for choosing to save this historic bridge from certain doom!