S 91 over Boulder River
Fair Condition88 years old2,133 vehicles/day
Location
| State | Montana |
| County | Sweet Grass |
| Location | Big Timber |
| Carries | S 91 |
| Crosses | Boulder River |
| Coordinates | 45.83479, -109.93581 |
Condition Ratings
| Overall Condition | Fair |
| Deck | 5 (Fair) |
| Superstructure | 6 (Satisfactory) |
| Substructure | 5 (Fair) |
| Channel/Waterway | 7 (Good) |
| Scour Critical | 5 — Stable for scour |
Physical Characteristics
| Material | Steel Continuous |
| Design | Stringer/Multi-beam |
| Total Length | 285.8 ft (87.1 m) |
| Max Span | 89.9 ft (27.4 m) |
| Deck Width | 32.5 ft (9.9 m) |
| Deck Area | 862.3 sq m |
| Main Spans | 3 |
| Year Built | 1938 |
Traffic
| Avg Daily Traffic | 2,133 (2023) |
| Truck Traffic | 5% |
| Lanes On Bridge | 2 |
Inspection & Ownership
| Last Inspection | 723 |
| Inspection Frequency | Every 24 months |
| Owner | State Highway Agency |
| Historical Significance | Bridge is not eligible for the National Register |
| Structure Number | P00091002+06221 |