Mo 21 N over Rt M
FairJefferson County, Missouri · S 18 T 42 N R 5 E · Structure no. 4322
- Built
- 1997
- 28 years old
- Condition
- Fair
- inspected November 2024
- Type
- Stringer/Multi-beam or Girder
- Prestressed Concrete Continuous
- Length
- 282 ft
- 4 main spans
- Daily traffic
- 8,817
- 2024 count
- Owner
- State
- State Highway Agency
About this bridge
Mo 21 N over Rt M is a prestressed concrete continuous stringer/multi-beam or girder carrying Mo 21 N over Rt M in Jefferson County, Missouri. It was built in 1997, so it is 28 years old, younger than the Missouri average of 45.1 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 8,817 vehicles a day, roughly 3% of them trucks, projected to reach 14,989 by 2044. The structure is 282 ft (86 m) long and 51 ft wide. If it were closed, the detour would be 1.2 mi (2 km).
Location
Open in Google MapsCondition and inspection
The lowest-rated primary component is rated 5 or 6. Minor deterioration is present but the structure is sound.
| Component | Rating | Meaning |
|---|---|---|
| Deck | 6 Satisfactory | Structural elements show some minor deterioration. |
| Superstructure | 7 Good | Some minor problems. |
| Substructure | 8 Very Good | No problems noted. |
Structure
Traffic and service
Ownership and planned work
Frequently asked questions
When was Mo 21 N over Rt M built?
It was built in 1997, making it 28 years old in 2025.
What condition is Mo 21 N over Rt M 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 November 2024.
How much traffic does Mo 21 N over Rt M carry?
About 8,817 vehicles per day (2024 count), of which roughly 3% are trucks.
How long is Mo 21 N over Rt M?
The structure is 282 ft (86 m) long with a longest span of 82 ft (25 m) and a deck 51 ft wide.
Who owns Mo 21 N over Rt M?
It is owned by the State Highway Agency.