US Bridges

Mt 41 over Beaverhead River

Fair

Madison County, Montana · Twin Bridges · Structure no. P00049027+05411

Built
1949
76 years old
Condition
Fair
inspected November 2024
Type
Stringer/Multi-beam or Girder
Steel
Length
181 ft
3 main spans
Daily traffic
2,865
2023 count
Owner
State
State Highway Agency

About this bridge

Mt 41 over Beaverhead River is a steel stringer/multi-beam or girder carrying Mt 41 over Beaverhead River in Madison County, Montana. It was built in 1949, so it is 76 years old, older than the Montana average of 47 years.

The most recent inspection reported to the Federal Highway Administration rates it in fair condition with a lowest component rating of 5 out of 9. The lowest-rated primary component is rated 5 or 6. Minor deterioration is present but the structure is sound.

It carries about 2,865 vehicles a day, roughly 10% of them trucks, projected to reach 3,051 by 2043. The structure is 181 ft (55.2 m) long and 36 ft wide. If it were closed, the detour would be 95.1 mi (153 km).

Location

Open in Google Maps
CarriesMt 41
CrossesBeaverhead River
LocationTwin Bridges
RouteState Highway 41
CountyMadison County
StateMontana
Coordinates45.54426, -112.33248
Functional classRural Principal Arterial - Other

Condition and inspection

Fair

The lowest-rated primary component is rated 5 or 6. Minor deterioration is present but the structure is sound.

ComponentRatingMeaning
Deck7 GoodSome minor problems.
Superstructure6 SatisfactoryStructural elements show some minor deterioration.
Substructure5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Channel and channel protection4 PoorAdvanced section loss, deterioration, spalling or scour.
Last inspectionNovember 2024
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourScour critical; foundations unstable for calculated scour conditions
Structural evaluation5: Somewhat better than minimum adequacy to tolerate being left in place as is
Deck geometry4: Meets minimum tolerable limits to be left in place as is
Waterway adequacy8: Equal to present desirable criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating43 US tons
Inventory rating33 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialSteel
DeckConcrete, cast-in-place
Main spans3
Design loadHS 15
Structure length181 ft (55.2 m)
Longest span60 ft (18.4 m)
Deck width36 ft (11 m)
Roadway width28 ft (8.5 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic2,865 (2023)
Projected traffic3,051 by 2043
Trucks10%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway and pedestrian
CrossesWaterway
Detour if closed95.1 mi (153 km)
TollOn a free road
National Highway SystemYes

Ownership and planned work

OwnerState Highway Agency
Maintained byState Highway Agency
Historic statusNot eligible for the National Register of Historic Places
Work proposedNone recorded
Estimated improvement cost—
NavigationNo navigation control on waterway

Frequently asked questions

When was Mt 41 over Beaverhead River built?

It was built in 1949, making it 76 years old in 2025.

What condition is Mt 41 over Beaverhead River in?

The National Bridge Inventory rates it in fair condition. The lowest-rated primary component is rated 5 or 6. Minor deterioration is present but the structure is sound. The last reported inspection was in November 2024.

How much traffic does Mt 41 over Beaverhead River carry?

About 2,865 vehicles per day (2023 count), of which roughly 10% are trucks.

How long is Mt 41 over Beaverhead River?

The structure is 181 ft (55.2 m) long with a longest span of 60 ft (18.4 m) and a deck 36 ft wide.

Who owns Mt 41 over Beaverhead River?

It is owned by the State Highway Agency.