Old US 91 over Missouri River-rr 069
Cascade County, Montana · rated Poor in the 2025 National Bridge Inventory
United States Bridge Conditions2025 National Bridge Inventory, FHWACompiled
- Old US 91 over Missouri River-rr 069 in Cascade County, Montana, is rated in poor condition in the 2025 National Bridge Inventory (as of ).
- Its lowest-rated component is the superstructure, rated 4 (poor condition) on the 0-9 scale.
- It was built in 1931, making it 94 years old at the 2025 inventory.
- It carries about 316 vehicles a day (traffic count year 2023).
- Its listed owner is the state highway agency.
- It is one of 11 of the 185 inventoried bridges in Cascade County rated poor (5.9%); 11 (5.9%) are rated poor.
- Its traffic status in the 2025 inventory is open, no restriction (NBI item 41).
- It was rated fair in the 2024 inventory and is now poor (superstructure 5 to 4).
- Its most recent inspection on record is dated July 2024, on a 24-month routine inspection cycle.
- It has fracture-critical members (NBI item 92A): steel tension members without a redundant load path, which get their own scheduled inspections.
- A poor rating means at least one major component - deck, superstructure, or substructure - is rated 4 or lower on FHWA's 0-9 scale. It does not by itself mean the bridge is unsafe; bridges judged unsafe are closed or load-restricted by their owners.
View this bridge on a map → (47.16701, -111.83439)
Component ratings
| Component | Rating (2024) | Rating (2025) | FHWA scale meaning |
|---|---|---|---|
| Deck | 5 | 5 | Fair condition |
| Superstructure | 5 | 4 | Poor condition |
| Substructure | 6 | 6 | Satisfactory condition |
Bridge details
| Structure | Steel through truss |
| Length | about 549 ft |
| Location | 11M S Cascade |
| NBI structure number | L07604006+04001 |
| Condition class | Poor |
| Traffic status (item 41) | Open, no restriction |
| Last inspection (item 90) | July 2024 |
| Inspection interval (item 91) | 24 months |
| Scour (item 113) | 5: foundations stable, scour within the limits of the footing or piles |
| Fracture critical (item 92A) | Yes |
Source: FHWA National Bridge Inventory, 2025 data as reported by the Montana department of transportation.
Busiest bridges in Cascade County
| Bridge | Built | Vehicles/day | Condition |
|---|---|---|---|
| Central Ave over Missouri River-ped Trail | 1980 | 24,549 | Good |
| 15TH St N-us 87 over Missouri R-rivers Trail | 1962 | 14,369 | Fair |
| 9TH St N over Missouri River | 1996 | 14,024 | Fair |
| 6TH St SW over Sun River | 1980 | 13,800 | Fair |
| US 87-mt 3-mt 200 over Missouri River-u5205-rr | 1983 | 13,666 | Fair |
| US 89-mt 3-mt 200 over Missouri River-u5205-rr | 1951 | 13,666 | Fair |
All bridges nearby: Cascade County, MT bridge conditions · every bridge in Cascade County · Montana bridges.
Background: how bridge ratings work · what "poor" and "structurally deficient" actually mean · how often bridges are inspected.