| Special Bridge Conditions Legend |
| ! | Confirmed demolition date within one year or an especially historic bridge that is threatened with demolition at any level. |
| X | The bridge has been confirmed demolished or collapsed. |
| S | The bridge has been dismantled or moved to an offsite location and is not currently available for public viewing. |
| L | Most or all of the original bridge material has been demolished and replaced, including historically significant elements, but some original parts of the bridge remain. |
| Note: This website cannot guarantee the current condition of any bridge on this website. Bridges lacking these icons should not necessarily be considered condition-free. |
| Bridge Name | HSR Rating | Facility Carried / Feature Intersected | Location | Structure Type | Structure Dimensions | Construction Date / Builder or Contractor | Description | Thumbnail |
Agate Falls Bridge
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 | M-28 Over Middle Branch Ontonagon River | Rural: Ontonagon County, Michigan | Metal Two-Hinged Solid Ribbed Deck Arch, Fixed and Approach Spans: Concrete Slab, Fixed |
Total Length: 193 ft Main Span Length: 150 ft Roadway Width: 32.2 ft Main Spans: 1 |
1930 By: Meads and Anderson and Michigan State Highway Department | This magnificent arch bridge is the older and more ornate of two distinctive steel deck arch bridges in the Upper Penninsula. | 
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Agate Falls Railroad Bridge
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 | Railroad (Bergland to Sidnaw Rail Trail / Trail 8) Over Middle Branch Ontonagon River | Rural: Ontonagon County, Michigan | Metal Deck Girder, Fixed | 1900 By: American Bridge Company of New York, New York | This impressive high level bridge is one of the earliest bridges built by the prolific American Bridge Company. | 
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Baltimore River Railroad Bridge
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 | Railroad (Bergland to Sidnaw Rail Trail / Trail 8) Over Baltimore River | Rural: Ontonagon County, Michigan | Metal Deck Girder, Fixed |
Total Length: 435 ft Roadway Width: 8 ft Main Spans: 13 |
1899 By: Lassig Bridge and Iron Works of Chicago, Illinois | This plate girder with steel bents for support carries a former railroad line over a shallow river valley. | 
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M-26 West Branch Firesteel River Bridge
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 | M-26 Over West Branch Firesteel River | Rural: Ontonagon County, Michigan | Metal Cantilever Deck Girder, Fixed |
Total Length: 270 ft Main Span Length: 102 ft Roadway Width: 28 ft Main Spans: 3 |
1952 By: Unknown and Michigan State Highway Department | One of several examples of a Michigan cantilevered haunched deck plate girder in this area. | 
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M-38 Bridge
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| M-38 Over West Branch Firesteel River | Rural: Ontonagon County, Michigan | Metal Cantilever Deck Girder, Fixed |
Total Length: 240 ft Main Span Length: 90 ft Roadway Width: 31 ft Main Spans: 3 |
1958 By: Jackson Construction Company and Michigan State Highway Department | An example of a Michigan standard riveted haunched deck plate girder with cantilevers and a suspended span. | 
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Old East Shore Road Bridge
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 | East Shore Road (Old Alignment) Over West Branch Ontonagon River | Rural: Ontonagon County, Michigan | Metal 3 Panel Rivet-Connected Warren Pony Truss, Fixed | Main Spans: 1 | By: Unknown | This is a small Warren pony truss, a bridge type that is uncommon in this region. | 
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Old M-26 West Branch Firesteel River Bridge
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| Old M-26 Over West Branch Firesteel River | Rural: Ontonagon County, Michigan | Concrete Closed Spandrel Deck Arch, Fixed |
Total Length: 35 ft Main Spans: 1 |
1922 By: Unknown and Michigan State Highway Department | This is an unusual arch bridge that sits buried in the woods on a long-abandoned alignment of M-26. | 
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Ontonagon Railroad Bridge
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| Railroad (Escanaba and Lake Superior Railroad) Over Ontonagon River | Ontonagon: Ontonagon County, Michigan | Metal 6 Panel Pin-Connected Pratt Full-Slope Pony Truss, Fixed and Approach Spans: Metal Deck Girder, Fixed |
Total Length: 470 ft Main Span Length: 100 ft Roadway Width: 15 ft Main Spans: 2 |
1899 By: Lassig Bridge and Iron Works of Chicago, Illinois | A rare and early surviving example of a multi-span railroad pony truss bridge. | 
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US-45 East Branch Ontonagon River Bridge
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 | US-45 Over East Branch Ontonagon River | Rural: Ontonagon County, Michigan | Metal Continuous Deck Girder, Fixed |
Total Length: 384 ft Main Span Length: 144 ft Roadway Width: 35 ft Main Spans: 3 |
1958 By: Jackson Construction Company and Michigan State Highway Department | An example of a haunched deck plate girder designed by the Michigan State Highway Department. | 
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