US Bridges

Old US 91 over Missouri River-Rr 069

Poor

Cascade County, Montana · 11M S Cascade · Structure no. L07604006+04001

Built
1931
94 years old
Condition
Poor
inspected July 2024
Type
Truss - Thru
Steel
Length
550 ft
3 main spans
Daily traffic
316
2023 count
Owner
State
State Highway Agency

About this bridge

Old US 91 over Missouri River-Rr 069 is a steel truss - thru carrying Old US 91 over Missouri River-Rr 069 in Cascade County, Montana. It was built in 1931, so it is 94 years old, older than the Montana average of 47 years.

The most recent inspection reported to the Federal Highway Administration rates it in poor condition with a lowest component rating of 4 out of 9. The lowest-rated primary component is rated 4 or below, indicating advanced deterioration. Poor does not mean unsafe; such bridges are inspected more often and may carry load restrictions.

It carries about 316 vehicles a day, roughly 2% of them trucks, projected to reach 332 by 2043. The structure is 550 ft (167.6 m) long and 21 ft wide. If it were closed, the detour would be 8.7 mi (14 km).

Location

Open in Google Maps
CarriesOld US 91
CrossesMissouri River-Rr 069
Location11M S Cascade
RouteState Highway 81003
CountyCascade County
StateMontana
Coordinates47.16701, -111.83439
Functional classRural Major Collector

Condition and inspection

Poor

The lowest-rated primary component is rated 4 or below, indicating advanced deterioration. Poor does not mean unsafe; such bridges are inspected more often and may carry load restrictions.

ComponentRatingMeaning
Deck5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Superstructure4 PoorAdvanced section loss, deterioration, spalling or scour.
Substructure6 SatisfactoryStructural elements show some minor deterioration.
Channel and channel protection7 GoodSome minor problems.
Last inspectionJuly 2024
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; scour within limits of footing or piles
Structural evaluation4: Meets minimum tolerable limits to be left in place as is
Deck geometry3: Basically intolerable, requiring high priority of corrective action
Waterway adequacy8: Equal to present desirable criteria
Approach roadway alignment4: Meets minimum tolerable limits to be left in place as is
Operating rating41 US tons
Inventory rating24 US tons

Structure

Structure typeTruss - Thru
MaterialSteel
DeckConcrete, cast-in-place
Main spans3 (+1 approach)
Design loadH 15
Structure length550 ft (167.6 m)
Longest span199 ft (60.8 m)
Deck width21 ft (6.3 m)
Roadway width20 ft (6 m)
Vertical clearance over deck14 ft (4.3 m)

Traffic and service

Average daily traffic316 (2023)
Projected traffic332 by 2043
Trucks2%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesRailroad and waterway
Detour if closed8.7 mi (14 km)
TollOn a free road
National Highway SystemNo

Ownership and planned work

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

Frequently asked questions

When was Old US 91 over Missouri River-Rr 069 built?

It was built in 1931, making it 94 years old in 2025.

What condition is Old US 91 over Missouri River-Rr 069 in?

The National Bridge Inventory rates it in poor condition. The lowest-rated primary component is rated 4 or below, indicating advanced deterioration. Poor does not mean unsafe; such bridges are inspected more often and may carry load restrictions. The last reported inspection was in July 2024.

How much traffic does Old US 91 over Missouri River-Rr 069 carry?

About 316 vehicles per day (2023 count), of which roughly 2% are trucks.

How long is Old US 91 over Missouri River-Rr 069?

The structure is 550 ft (167.6 m) long with a longest span of 199 ft (60.8 m) and a deck 21 ft wide.

Who owns Old US 91 over Missouri River-Rr 069?

It is owned by the State Highway Agency.