18131: Maiden Rock over Big Hole River
Silver Bow County, Montana · rated Fair in the 2025 National Bridge Inventory
United States Bridge Conditions2025 National Bridge Inventory, FHWACompiled
- 18131: Maiden Rock over Big Hole River in Silver Bow County, Montana, is rated in fair condition in the 2025 National Bridge Inventory (as of ).
- Its lowest-rated component is the superstructure, rated 5 (fair condition) on the 0-9 scale.
- It was built in 1951 and reconstructed in 1993, making it 74 years old at the 2025 inventory.
- It carries about 25 vehicles a day (traffic count year 2022).
- It is one of 57 of the 70 inventoried bridges in Silver Bow County rated fair (81.4%); 2 (2.9%) 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.
View this bridge on a map → (45.70152, -112.73534)
Component ratings
| Component | Rating (2025) | FHWA scale meaning |
|---|---|---|
| Deck | 6 | Satisfactory condition |
| Superstructure | 5 | Fair condition |
| Substructure | 7 | Good condition |
Bridge details
| Structure | Steel through truss |
| Length | about 202 ft |
| Location | 24 mi SW of Butte MT |
| NBI structure number | 000000000L59197 |
| Condition class | Fair |
Source: FHWA National Bridge Inventory, 2025 data as reported by the Montana department of transportation.
Busiest bridges in Silver Bow County
| Bridge | Built | Vehicles/day | Condition |
|---|---|---|---|
| I 15 over Bell Creek | 1963 | 19,755 | Fair |
| I-90 E&w over Abandoned Railroad | 2019 | 15,011 | Good |
| S Montana St over Silver Bow Creek | 1970 | 14,718 | Fair |
| I 15 over Int Rocker | 1968 | 10,824 | Fair |
| I 15 over Int Rocker | 1968 | 10,824 | Fair |
| I 90 over Whitetail Creek | 1965 | 10,349 | Fair |
All bridges nearby: Silver Bow County, MT bridge conditions · every bridge in Silver Bow County · Montana bridges.
Background: how bridge ratings work · what "poor" and "structurally deficient" actually mean · how often bridges are inspected.