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Ross Fork Road over Middle Fork Rock CR 021

Granite County, Montana · rated Good in the 2025 National Bridge Inventory

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

Ross Fork Road over Middle Fork Rock CR 021 in Granite County, Montana, is rated in good condition in the 2025 National Bridge Inventory (as of August 20, 2026).
Its lowest-rated component is the deck, rated 8 (very good condition) on the 0-9 scale.
It was built in 1991, making it 34 years old at the 2025 inventory.
It carries about 100 vehicles a day (traffic count year 2025).
Its listed owner is the county highway agency.
It is one of 28 of the 73 inventoried bridges in Granite County rated good (38.4%); 9 (12.3%) are rated poor.
A good rating means every major component - deck, superstructure, substructure, or culvert - is rated 7 or higher on FHWA's 0-9 scale: no more than minor problems.

Component ratings


Structure	Prestressed concrete stringer or multi-beam girder
Length	about 82 ft
Location	15M SW Phillipsburg
NBI structure number	L20067000+04001
Condition class	Good

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

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