US Bridges

I-39/US 51 over Mackinaw River

Fair

McLean County, Illinois · 8.8 MI N of I-55 · Structure no. 057020300000000

Built
1989
36 years old
Condition
Fair
inspected March 2024
Type
Stringer/Multi-beam or Girder
Steel Continuous
Length
432 ft
3 main spans
Daily traffic
18,700
2023 count
Owner
State
State Highway Agency

About this bridge

I-39/US 51 over Mackinaw River is a steel continuous stringer/multi-beam or girder carrying I-39/US 51 over Mackinaw River in McLean County, Illinois. It was built in 1989, so it is 36 years old, younger than the Illinois average of 45.3 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 18,700 vehicles a day, roughly 37% of them trucks, projected to reach 18,281 by 2046. The structure is 432 ft (131.6 m) long and 93 ft wide. If it were closed, the detour would be 1.2 mi (2 km).

Location

Open in Google Maps
CarriesI-39/US 51
CrossesMackinaw River
Location8.8 MI N of I-55
RouteInterstate 39
CountyMcLean County
StateIllinois
Coordinates40.66284, -89.00519
Functional classRural Principal Arterial - Interstate

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 inspectionMarch 2024
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; scour within limits of footing or piles
Structural evaluation6: Equal to present minimum criteria
Deck geometry9: Superior to present desirable criteria
Waterway adequacy8: Equal to present desirable criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating44.6 US tons
Inventory rating26.8 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialSteel Continuous
DeckConcrete, cast-in-place
Main spans3
Design loadHS 20
Structure length432 ft (131.6 m)
Longest span163 ft (49.7 m)
Deck width93 ft (28.4 m)
Roadway width88 ft (26.7 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic18,700 (2023)
Projected traffic18,281 by 2046
Trucks37%
Lanes on structure4
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed1.2 mi (2 km)
TollOn a free road
National Highway SystemYes
Strategic Highway NetworkInterstate STRAHNET route

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 I-39/US 51 over Mackinaw River built?

It was built in 1989, making it 36 years old in 2025.

What condition is I-39/US 51 over Mackinaw 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 March 2024.

How much traffic does I-39/US 51 over Mackinaw River carry?

About 18,700 vehicles per day (2023 count), of which roughly 37% are trucks.

How long is I-39/US 51 over Mackinaw River?

The structure is 432 ft (131.6 m) long with a longest span of 163 ft (49.7 m) and a deck 93 ft wide.

Who owns I-39/US 51 over Mackinaw River?

It is owned by the State Highway Agency.