18131: MAIDEN ROCK
Carrying 18131: MAIDEN ROCK over Big Hole River
24 mi SW of Butte, MT, Silver Bow, Montana
Data updated May 2026
FHWA NBI record, refreshed with each annual release.
Bridge Snapshot: 18131: MAIDEN ROCK
The 18131: MAIDEN ROCK bridge in Silver Bow, Montana carries 18131: MAIDEN ROCK over Big Hole River. It was built in 1951, making it 75 years old today. It was last reconstructed in 1993, extending its service life. The structure is built primarily of steel and spans 1 section, stretching 61.6 meters (202 feet) end to end. Daily traffic averages 25 vehicles, placing it in the lower-traffic tier of Montana bridges. It is owned and maintained by Bureau of Land Management.
The latest FHWA inspection records show a deck rating of 6/9, superstructure at 5/9, substructure at 7/9. 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 21.4 metric tons.
Sourced from the FHWA National Bridge Inventory. See our methodology for refresh cadence and NBI release vintage.
How 18131: MAIDEN ROCK 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 How the historical reference is calculated.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
- 1951
- Last Reconstructed
- 1993
- Material
- Steel
- Number of Spans
- 1
- Structure Length
- 61.6 m (202 ft)
- Deck Width
- 6.4 m (21 ft)
- Owner
- Bureau of Land Management
- Avg Daily Traffic
- 25 vehicles/day
- Structure Number
- 000000000L59197
Location
Data Source
FHWA National Bridge Inventory (NBI).
FHWA NBI Program ↗Condition Analysis
- • The deck (driving surface) is in fair condition (6/9), with minor deterioration that may require routine maintenance.
- • The superstructure (beams and supports above the deck) is in fair condition (5/9), with minor deterioration that may require routine maintenance.
- • The substructure (piers and abutments) rates good at 7/9, with no significant deterioration on file.
How to read this record
This page shows what the last federal inspection recorded, not whether 18131: MAIDEN ROCK 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 18131: MAIDEN ROCK against other structures in Silver Bow 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 18131: MAIDEN ROCK?
18131: MAIDEN ROCK in Silver Bow, Montana has a deck rating of 6/9, superstructure rating of 5/9, and substructure rating of 7/9 on the FHWA's 0–9 scale.
How often is 18131: MAIDEN ROCK inspected?
18131: MAIDEN ROCK'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 25 vehicles per day.
What does “structurally deficient” mean in older bridge reports?
FHWA retired that reported status beginning with the 2018 archive. 18131: MAIDEN ROCK 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 18131: MAIDEN ROCK?
18131: MAIDEN ROCK has an NBI inventory load rating of 21.4 metric tons.
Who is responsible for maintaining 18131: MAIDEN ROCK?
18131: MAIDEN ROCK is owned and maintained by Bureau of Land Management.
How old is 18131: MAIDEN ROCK and does age affect safety?
18131: MAIDEN ROCK was built in 1951, making it 75 years old and last reconstructed in 1993.
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.