US Bridges

US 287 over Dearborn River

Fair

Lewis and Clark County, Montana · 14M NW Wolf Creek · Structure no. P00009013+00501

Built
1963
62 years old
Condition
Fair
inspected August 2023
Type
Stringer/Multi-beam or Girder
Steel Continuous
Length
299 ft
3 main spans
Daily traffic
460
2023 count
Owner
State
State Highway Agency

About this bridge

US 287 over Dearborn River is a steel continuous stringer/multi-beam or girder carrying US 287 over Dearborn River in Lewis and Clark County, Montana. It was built in 1963, so it is 62 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 6 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 460 vehicles a day, roughly 9% of them trucks, projected to reach 483 by 2043. The structure is 299 ft (91.1 m) long and 32 ft wide. If it were closed, the detour would be 60.9 mi (98 km).

Location

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CarriesUS 287
CrossesDearborn River
Location14M NW Wolf Creek
RouteU.S. Route 287
CountyLewis and Clark County
StateMontana
Coordinates47.19873, -112.0959
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.
Superstructure7 GoodSome minor problems.
Substructure7 GoodSome minor problems.
Channel and channel protection7 GoodSome minor problems.
Last inspectionAugust 2023
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 geometry5: Somewhat better than minimum adequacy to tolerate being left in place as is
Waterway adequacy8: Equal to present desirable criteria
Approach roadway alignment7: Better than present minimum criteria
Operating rating28 US tons
Inventory rating22 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialSteel Continuous
DeckConcrete, cast-in-place
Main spans3
Design loadHS 20
Structure length299 ft (91.1 m)
Longest span113 ft (34.4 m)
Deck width32 ft (9.7 m)
Roadway width28 ft (8.5 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic460 (2023)
Projected traffic483 by 2043
Trucks9%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed60.9 mi (98 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 proposedNone recorded
Estimated improvement cost—
NavigationNo navigation control on waterway

Frequently asked questions

When was US 287 over Dearborn River built?

It was built in 1963, making it 62 years old in 2025.

What condition is US 287 over Dearborn 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 August 2023.

How much traffic does US 287 over Dearborn River carry?

About 460 vehicles per day (2023 count), of which roughly 9% are trucks.

How long is US 287 over Dearborn River?

The structure is 299 ft (91.1 m) long with a longest span of 113 ft (34.4 m) and a deck 32 ft wide.

Who owns US 287 over Dearborn River?

It is owned by the State Highway Agency.