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M-33 over Thunder Bay River

Montmorency County, Michigan · rated Fair in the 2025 National Bridge Inventory

United States Bridge Conditions2025 National Bridge Inventory, FHWACompiled August 20, 2026

M-33 over Thunder Bay River in Montmorency County, Michigan, is rated in fair condition in the 2025 National Bridge Inventory (as of August 20, 2026).
Its lowest-rated component is the substructure, rated 6 (satisfactory condition) on the 0-9 scale.
It was built in 1968, making it 57 years old at the 2025 inventory.
It carries about 1,647 vehicles a day (traffic count year 2007).
Its listed owner is the state highway agency.
It is one of 8 of the 21 inventoried bridges in Montmorency County rated fair (38.1%); 0 (0.0%) are rated poor.
A fair rating means the lowest-rated major component scores 5 or 6 on FHWA's 0-9 scale: some deterioration or minor section loss, but the structure is sound. It is the middle class, not a warning.

Component ratings


Structure	Steel stringer or multi-beam girder
Length	about 65 ft
Location	1.5 Mi S of M-32
NBI structure number	000000000007536
Condition class	Fair

Source: FHWA National Bridge Inventory, 2025 data as reported by the Michigan department of transportation.

Bridge	Built	Vehicles/day	Condition
M-32 Bs\|s State St over Thunder Bay River	2009	6,400	Fair
M-32 over Miller Creek	1991	4,572	Fair
M-32 over Thunder Bay River	1927	4,572	Fair
Co Road 451 over N Br Thunder Bay River	1994	2,126	Fair
M-33 over Gilchrist Creek	1951	1,647	Fair
Airport Road over Thunder Bay River	1969	160	Good