US Bridges

US 191 over Yellowstone River

Fair

Sweet Grass County, Montana · 1M N Big Timber · Structure no. P00045000+09831

Built
1938
87 years old
Condition
Fair
inspected September 2024
Type
Girder and Floorbeam System
Steel Continuous
Length
380 ft
3 main spans
Daily traffic
1,699
2023 count
Owner
State
State Highway Agency

About this bridge

US 191 over Yellowstone River is a steel continuous girder and floorbeam system carrying US 191 over Yellowstone River in Sweet Grass County, Montana. It was built in 1938, so it is 87 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 1,699 vehicles a day, roughly 5% of them trucks, projected to reach 1,784 by 2043. The structure is 380 ft (115.8 m) long and 28 ft wide. If it were closed, the detour would be 9.9 mi (16 km).

Location

Open in Google Maps
CarriesUS 191
CrossesYellowstone River
Location1M N Big Timber
RouteU.S. Route 191
CountySweet Grass County
StateMontana
Coordinates45.84685, -109.9399
Functional classRural Minor Arterial

Condition and inspection

Fair

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

ComponentRatingMeaning
Deck6 SatisfactoryStructural elements show some minor deterioration.
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 protection7 GoodSome minor problems.
Last inspectionSeptember 2024
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; scour within limits of footing or piles
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 adequacy9: Superior to present desirable criteria
Approach roadway alignment6: Equal to present minimum criteria
Operating rating48 US tons
Inventory rating29 US tons

Structure

Structure typeGirder and Floorbeam System
MaterialSteel Continuous
DeckConcrete, cast-in-place
Main spans3 (+2 approach)
Design loadH 15
Structure length380 ft (115.8 m)
Longest span122 ft (37.2 m)
Deck width28 ft (8.4 m)
Roadway width24 ft (7.3 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic1,699 (2023)
Projected traffic1,784 by 2043
Trucks5%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed9.9 mi (16 km)
TollOn a free road
National Highway SystemNo

Ownership and planned work

OwnerState Highway Agency
Maintained byState Highway Agency
Historic statusNot eligible for the National Register of Historic Places
Work proposedReplacement because of substandard load-carrying capacity or roadway geometry
Estimated improvement cost$938,000
NavigationNo navigation control on waterway

Frequently asked questions

When was US 191 over Yellowstone River built?

It was built in 1938, making it 87 years old in 2025.

What condition is US 191 over Yellowstone 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 September 2024.

How much traffic does US 191 over Yellowstone River carry?

About 1,699 vehicles per day (2023 count), of which roughly 5% are trucks.

How long is US 191 over Yellowstone River?

The structure is 380 ft (115.8 m) long with a longest span of 122 ft (37.2 m) and a deck 28 ft wide.

Who owns US 191 over Yellowstone River?

It is owned by the State Highway Agency.