Structure 2456 · Emmet County, MI
Carries I-75 over Straits Of Mackinac, Mackinaw City-st Ignace.
Set by its lowest-rated component: Deck and Superstructure at 6 of 9.
How ratings work19,248 ft end to end, longest span 3,801 ft: about 53 football fields, or 3.6 miles. Lengths are drawn to scale; at this length a semi-truck would be a speck. Each part is colored by its latest inspection rating. The inventory records lengths but not heights or the layout of the shorter spans, so those are drawn as typical for a suspension bridge.
| State | Michigan |
| County | Emmet |
| Location | Mackinaw City-st Ignace |
| Carries | I-75 |
| Crosses | Straits Of Mackinac |
| Coordinates | 45.83684, -84.72481 |
| Material | Steel |
| Design | Suspension |
| Total Length | 19247.7 ft (5866.7 m) |
| Max Span | 3800.9 ft (1158.5 m) |
| Deck Width | 53.8 ft (16.4 m) |
| Deck Area | 96213.9 sq m |
| Main Spans | 3 |
| Year Built | 1957 |
| Avg Daily Traffic | 11,926 (2021) |
| Truck Traffic | 7% |
| Lanes On Bridge | 4 |
| Last Inspection | July 2024 |
| Inspection Frequency | Every 12 months |
| Owner | State Toll Authority |
| Historical Significance | Bridge is on the National Register of Historic Places |
| Scour Critical | 8 — Stable, low risk |
| Structure Number | 000000000002456 |
Inspectors rate each major part of a bridge (the deck you drive on, the superstructure of beams that holds it up, and the substructure of piers and abutments beneath) on a 0–9 scale. A bridge's overall condition is its lowest of those ratings, so one deteriorated component makes the whole bridge "poor."
A poor rating is not a closure. It means the bridge is flagged for priority repair or replacement; bridges judged unsafe are closed or posted with weight limits. The waterway (channel) rating is reported, but it does not count toward the overall classification.