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S 556-thompson R R over Big Rock Creek

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

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

S 556-thompson R R over Big Rock Creek in Sanders 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 7 (good condition) on the 0-9 scale.
It was built in 2009, making it 16 years old at the 2025 inventory.
It carries about 56 vehicles a day (traffic count year 2023).
Its listed owner is the county highway agency.
It is one of 45 of the 120 inventoried bridges in Sanders County rated good (37.5%); 10 (8.3%) 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 tee beam
Length	about 49 ft
Location	35M SW Marion
NBI structure number	S00556028+01001
Condition class	Good

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

Bridge	Built	Vehicles/day	Condition
S 200 over Clark Fork River	1997	3,009	Fair
S 200 over Clark Fork River	1996	3,009	Fair
S 200 over RR	2000	2,686	Good
S 200 over Clark Fork River	1960	2,482	Poor
Irr - S 28 over Hot Springs Creek	1959	2,181	Fair
S 200 over Wildlife Crossing	2019	2,177	Good