Bridge conditions in Granite County, Montana
73 inventoried bridges · 9 rated poor · 2025 National Bridge Inventory
United States Bridge Conditions2025 National Bridge Inventory, FHWACompiled
Of the 73 Granite County bridges in the federal inventory, 9 carry a poor rating. That 12.3% share is roughly 2x the national average.
- 9 of the 73 bridges in Granite County, Montana, are rated in poor condition (12.3%) in the 2025 National Bridge Inventory, as of .
- 28 bridges (38.4%) are rated good and 36 (49.3%) fair.
- The median Granite County bridge was built in 1970.
- The busiest poor-rated bridge is I 90 over Clark Fork River (built 1970), carrying about 13,081 vehicles a day.
Good 38.4% · Fair 49.3% · Poor 12.3% of 73 bridges
Bridges rated poor
Every bridge in the county with a poor rating, busiest first. Poor means a major component is rated 4 or lower on FHWA's 0-9 scale; it is a repair flag, not a closure notice.
| Bridge | Built | Vehicles/day | Condition |
|---|---|---|---|
| I 90 over Clark Fork River | 1970 | 13,081 | Poor |
| S 1 over Clark Fork | 1966 | 1,354 | Poor |
| S Main Street over Clark Fork River 020 | 1934 | 371 | Poor |
| Marshall Creek Rd over Rock Creek | 1959 | 161 | Poor |
| Bear Gulch Rd over Clark Fork River 002 | 1986 | 130 | Poor |
| I 90 over Antelope Creek | 1971 | 100 | Poor |
| No Data Entered over Ross Fork | 1967 | 50 | Poor |
| No Data Entered over Swamp Gul | 1987 | 50 | Poor |
| No Data Entered over Boulder CR | 1949 | 50 | Poor |
Busiest bridges in the county
| Bridge | Built | Vehicles/day | Condition |
|---|---|---|---|
| I 90 over Harvey Creek | 1970 | 13,081 | Good |
| I 90 over Drainage | 1971 | 13,081 | Good |
| I 90 over Sep Bearmouth Road | 1970 | 13,081 | Good |
| I 90 over Clark Fork River | 1970 | 13,081 | Poor |
| I 90 over Rattler Gulch | 1971 | 13,081 | Fair |
| I 90 over Clark Fork River | 1970 | 11,802 | Fair |
| I 90 over Int Bearmouth | 1970 | 6,541 | Fair |
| I 90 over Int Bearmouth | 1970 | 6,541 | Good |
| I 90 over Int E Drummond | 1966 | 4,666 | Fair |
| I 90 over Int E Drummond | 1966 | 4,666 | Good |
Source: FHWA National Bridge Inventory, 2025. Counts cover inventoried highway bridges over 20 feet; ratings are reported by the state DOT.
All of Montana: Montana bridge conditions by county · every download on the data page.
Background: how bridge ratings work · what "poor" and "structurally deficient" actually mean · how often bridges are inspected.