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M-66 over Clam River

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

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

M-66 over Clam River in Missaukee 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 5 (fair condition) on the 0-9 scale.
It was built in 1929, making it 96 years old at the 2025 inventory.
It carries about 2,696 vehicles a day (traffic count year 2007).
Its listed owner is the state highway agency.
It is one of 15 of the 39 inventoried bridges in Missaukee County rated fair (38.5%); 4 (10.3%) 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 43 ft
Location	3.6 Mi N of Mcbain
NBI structure number	000000000007025
Condition class	Fair

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

Bridge	Built	Vehicles/day	Condition
M-55\|w Watergate R over Clam River	1973	5,113	Fair
M-55\|e Houghton La over W Br Muskegon River	1931	4,338	Fair
M-55\|e Houghton La over Muskegon River	1935	4,338	Fair
M-66\|w Stoney Corn over N Br Clam River	1933	4,081	Fair
M-66\|s Burkett Rd over Middle Br Clam River	1929	2,466	Fair
Forward Road over Clam River	1958	1,316	Poor