US Bridges

S 59 over Yellowstone River

Fair

Custer County, Montana · Miles City · Structure no. P00018001+00921

Built
1957
68 years old
Condition
Fair
inspected June 2023
Type
Girder and Floorbeam System
Steel Continuous
Length
976 ft
6 main spans
Daily traffic
2,949
2023 count
Owner
State
State Highway Agency

About this bridge

S 59 over Yellowstone River is a steel continuous girder and floorbeam system carrying S 59 over Yellowstone River in Custer County, Montana. It was built in 1957, so it is 68 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 2,949 vehicles a day, roughly 3% of them trucks, projected to reach 3,096 by 2043. The structure is 976 ft (297.5 m) long and 32 ft wide. If it were closed, the detour would be 123.7 mi (199 km).

Location

Open in Google Maps
CarriesS 59
CrossesYellowstone River
LocationMiles City
RouteState Highway 59
CountyCuster County
StateMontana
Coordinates46.42081, -105.8599
Functional classUrban Other Principal 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.
Superstructure5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Substructure6 SatisfactoryStructural elements show some minor deterioration.
Channel and channel protection6 SatisfactoryStructural elements show some minor deterioration.
Last inspectionJune 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 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 rating48 US tons
Inventory rating29 US tons

Structure

Structure typeGirder and Floorbeam System
MaterialSteel Continuous
DeckConcrete, cast-in-place
Main spans6 (+1 approach)
Design loadHS 20
Structure length976 ft (297.5 m)
Longest span180 ft (54.9 m)
Deck width32 ft (9.7 m)
Roadway width28 ft (8.5 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic2,949 (2023)
Projected traffic3,096 by 2043
Trucks3%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed123.7 mi (199 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 S 59 over Yellowstone River built?

It was built in 1957, making it 68 years old in 2025.

What condition is S 59 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 June 2023.

How much traffic does S 59 over Yellowstone River carry?

About 2,949 vehicles per day (2023 count), of which roughly 3% are trucks.

How long is S 59 over Yellowstone River?

The structure is 976 ft (297.5 m) long with a longest span of 180 ft (54.9 m) and a deck 32 ft wide.

Who owns S 59 over Yellowstone River?

It is owned by the State Highway Agency.