21 MILE RD
Carrying 21 MILE RD over N FK CROOKED CREEK 079
20M N BILLINGS, Yellowstone, Montana
Data updated May 2026
FHWA NBI record, refreshed with each annual release.
Bridge Snapshot: 21 MILE RD
The 21 MILE RD bridge in Yellowstone, Montana carries 21 MILE RD over N FK CROOKED CREEK 079. It was built in 1965, making it 61 years old today. The structure is built primarily of prestressed concrete and spans 1 section, stretching 7.3 meters (24 feet) end to end. Daily traffic averages 68 vehicles, placing it in the lower-traffic tier of Montana bridges. It is owned and maintained by County Highway Agency.
The latest FHWA inspection records show a deck rating of 7/9, superstructure at 7/9, substructure at 6/9. The weakest component sits in fair condition. No reported major component scores in the Poor range under the current federal condition thresholds. Its NBI inventory load rating is 24.5 metric tons.
Sourced from the FHWA National Bridge Inventory. See our methodology for refresh cadence and NBI release vintage.
How 21 MILE RD compares
Live comparison across Montana.
Historical Sufficiency Rating
PlainBridge-computedFHWA discontinued this calculated item; it does not determine current condition, funding eligibility, posting, or closure. How the historical reference is calculated.
Condition Ratings
Full 0–9 scale + sufficiency-rating breakdown: how condition ratings work.
Structural Details
- Year Built
- 1965
- Material
- Prestressed Concrete
- Number of Spans
- 1
- Structure Length
- 7.3 m (24 ft)
- Deck Width
- 7.7 m (25 ft)
- Owner
- County Highway Agency
- Avg Daily Traffic
- 68 vehicles/day
- Structure Number
- L56701018+03001
Location
Data Source
FHWA National Bridge Inventory (NBI).
FHWA NBI Program ↗Condition Analysis
- • At 7/9, the deck (driving surface) is in good shape and shows no significant wear.
- • The superstructure (beams and supports above the deck) rates good at 7/9, with no significant deterioration on file.
- • At 6/9, the substructure (piers and abutments) shows fair condition, with minor wear flagged for upkeep.
How to read this record
This page shows what the last federal inspection recorded, not whether 21 MILE RD is safe to cross today. Here is how to use it.
- NBI condition ratings reflect the latest record in this annual dataset, not a live status. Current routine inspection intervals are risk-based.
- Learn how the 0–9 condition scale and Good/Fair/Poor categories are defined. How condition ratings work
- Compare 21 MILE RD against other structures in Yellowstone and across Montana. Montana bridges
- Noticed visible damage or a safety concern? Report it to the agency that owns the bridge, or call 911 in an emergency. How to report a bridge
Condition codes come straight from the FHWA National Bridge Inventory and are not a real-time safety judgment. Only the owning agency, a state DOT, county, or other owner, can post, restrict, or close a bridge.
Frequently Asked Questions
What do the condition ratings mean for 21 MILE RD?
21 MILE RD in Yellowstone, Montana has a deck rating of 7/9, superstructure rating of 7/9, and substructure rating of 6/9 on the FHWA's 0–9 scale.
How often is 21 MILE RD inspected?
21 MILE RD's responsible agency sets its routine interval under FHWA's risk-based inspection rules; this page does not expose the scheduled interval. It carries about 68 vehicles per day.
What does “structurally deficient” mean in older bridge reports?
FHWA retired that reported status beginning with the 2018 archive. 21 MILE RD is currently shown as Fair condition from its component ratings; that category is not a live closure or safety decision.
What is the inventory load rating for 21 MILE RD?
21 MILE RD has an NBI inventory load rating of 24.5 metric tons.
Who is responsible for maintaining 21 MILE RD?
21 MILE RD is owned and maintained by County Highway Agency.
How old is 21 MILE RD and does age affect safety?
21 MILE RD was built in 1965, making it 61 years old.
Disclaimer: Bridge condition data is from the FHWA NBI and reflects the last reported inspection. A Poor condition rating is not a live declaration that a bridge is closed or unsafe for travel. For current closure, posting, or safety information, contact the responsible transportation agency.
Every figure on PlainBridge is rendered directly from federal source data, no number is typed in by an editor. This page draws directly on federal source data, no figure is typed in by an editor. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error.