Main Boulder Road over Boulder River

Park County, Montana · rated Poor in the 2025 National Bridge Inventory

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

• Main Boulder Road over Boulder River in Park County, Montana, is rated in poor condition in the 2025 National Bridge Inventory (as of August 20, 2026).
• Its lowest-rated component is the substructure, rated 3 (serious condition) on the 0-9 scale.
• It was built in 1950, making it 75 years old at the 2025 inventory.
• It carries about 157 vehicles a day (traffic count year 2023).
• Its listed owner is the county highway agency.
• It is one of 13 of the 126 inventoried bridges in Park County rated poor (10.3%); 13 (10.3%) are rated poor.
• Its traffic status in the 2025 inventory is closed to all traffic (NBI item 41).
• Its condition class and component ratings are unchanged from the 2024 inventory.
• Its most recent inspection on record is dated September 2024, on a 24-month routine inspection cycle.
• It is coded scour critical (NBI item 113 = 0): scour critical: bridge has failed and is closed to traffic.
• 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 → (45.24254, -110.26126)

Component ratings

Bridge details

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

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Background: how bridge ratings work · what "poor" and "structurally deficient" actually mean · how often bridges are inspected.