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I 90 over Sep County Road

Jefferson County, Montana · rated Fair in the 2025 National Bridge Inventory

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

I 90 over Sep County Road in Jefferson County, Montana, is rated in fair condition in the 2025 National Bridge Inventory (as of August 20, 2026).
Its lowest-rated component is the deck, rated 5 (fair condition) on the 0-9 scale.
It was built in 1969, making it 56 years old at the 2025 inventory.
It carries about 5,599 vehicles a day (traffic count year 2023).
Its listed owner is the state highway agency.
It is one of 103 of the 136 inventoried bridges in Jefferson County rated fair (75.7%); 7 (5.1%) 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

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

Bridge	Built	Vehicles/day	Condition
I 15 over Prickly Pear Creek	1969	5,987	Fair
I 15 over Prickly Pear Creek	1969	5,987	Fair
S 518 over Int Montana City-i 15	1968	5,885	Good
I 90 over Int Cardwell-s 359	1968	5,599	Fair
I 90 over Int Cardwell-s 359	1968	5,599	Fair
I 90 Eastbound over Boulder River	1968	5,599	Good