STH 21
Carrying STH 21 over IH 41
AT STH 21 INTERCHANGE, Winnebago, Wisconsin
Inventory: FHWA NBI 2024 · last ETL August 2026
FHWA NBI record, refreshed with each annual release.
STH 21 in Winnebago, Wisconsin sits above 32% of rated Wisconsin bridges on inventory load rating (32 t), while its 2012 build year is earlier than 12% of Winnebago's recorded-year cohort (263 bridges).
STH 21 in Winnebago, Wisconsin is rated Good in the FHWA's 2024 National Bridge Inventory. Built in 2012, it carries 3 rated components on the inspecting agency's 0-9 scale, and its weakest reported component scores 7. The lowest applicable rating sets the federal condition category, so this Good result describes the weakest reported component rather than the structure as a whole. No NBI category is a closure decision or a live crossing-safety verdict.
NBI record plate
Structure WI:B70025800000000
POST-2000 · PRESTRESS · MULTI-SPAN · DECK-LED · HEAVY-ADT · STANDARD-LOAD · CAT-GOOD
- POST-2000 2000+
- PRESTRESS Prestressed concrete
- MULTI-SPAN 2 spans
- DECK-LED Deck-led
- HEAVY-ADT Heavy ADT
- STANDARD-LOAD Standard load
- CAT-GOOD Good
Inspection-sheet codes from this record’s year, material family, spans, controlling component, ADT, inventory load, and NBI category, not a live closure verdict.
Bridge Snapshot: STH 21
The STH 21 bridge in Winnebago, Wisconsin carries STH 21 over IH 41. It was built in 2012, making it 14 years old today. The structure is built primarily of prestressed concrete continuous and spans 2 sections, stretching 45.7 meters (150 feet) end to end. Daily traffic averages 18,500 vehicles, placing it in the heavily-trafficked tier of Wisconsin bridges. It is owned and maintained by State Highway Agency.
The latest FHWA inspection records show a deck rating of 7/9, superstructure at 8/9, substructure at 8/9. The weakest component sits in good condition. No reported major component scores in the Poor range under the current federal condition thresholds.
How STH 21 compares
Age against the county: built in 2012, earlier than 32 of Winnebago's 263 bridges with a recorded construction year (12%), against a county median build year of 1999. This is one of the newer structures in its county.
Live comparison across Wisconsin bridges with a recorded inventory load rating (14,446 rated).
STH 21 vs every rated Wisconsin bridge
Inventory load rating (metric tons), FHWA NBI, this state
32 Top 68% higher than 32% of 14,446 bridges
rated Wisconsin bridges, bucketed by value
Each bar is a band; taller bars hold more bridges. The dashed line + filled bar mark this entry. Hover or tap any bar for its full count and share, and where it sits relative to this entry.
Source FHWA National Bridge Inventory · August 2026
Condition Ratings
Full 0–9 scale + sufficiency-rating breakdown: how condition ratings work.
Reported 0–9 component ratings from the FHWA NBI. The highlighted component is the lowest reported input to this record’s current condition category; it is not a closure or live crossing-safety decision.
Winnebago inventory by recorded NBI category
Exclusive Good/Fair/Poor bands across all 263 bridges in this county. Orthogonal to this structure's component profile above: a county catalog share, not a live crossing-safety verdict.
Structural Details
- Year Built
- 2012
- Material
- Prestressed Concrete Continuous
- Number of Spans
- 2
- Structure Length
- 45.7 m (150 ft)
- Deck Width
- 31.5 m (103 ft)
- Owner
- State Highway Agency
- Avg Daily Traffic
- 18,500 vehicles/day
- Structure Number
- B70025800000000
Condition Analysis
- • At 7/9, the deck (driving surface) is in good shape and shows no significant wear.
- • At 8/9, the superstructure (beams and supports above the deck) is in good shape and shows no significant wear.
- • At 8/9, the substructure (piers and abutments) is in good shape and shows no significant wear.
Location
Data Source
FHWA National Bridge Inventory (NBI).
FHWA NBI Program ↗How to read this record
This page shows what the last federal inspection recorded, not whether STH 21 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 STH 21 against other structures in Winnebago and across Wisconsin. Wisconsin 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 STH 21?
STH 21 in Winnebago, Wisconsin has a deck rating of 7/9, superstructure rating of 8/9, and substructure rating of 8/9 on the FHWA's 0–9 scale.
How often is STH 21 inspected?
STH 21'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 18,500 vehicles per day.
What does “structurally deficient” mean in older bridge reports?
FHWA retired that reported status beginning with the 2018 archive. STH 21 is currently shown as Good condition from its component ratings; that category is not a live closure or safety decision.
What is the inventory load rating for STH 21?
STH 21 has an NBI inventory load rating of 32.4 metric tons.
Who is responsible for maintaining STH 21?
STH 21 is owned and maintained by State Highway Agency.
How old is STH 21 and does age affect safety?
STH 21 was built in 2012, making it 14 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.
Share this inspection record
Send this source-bounded record or download its data card. An NBI condition category is not a closure or live crossing-safety verdict.
Every figure on PlainBridges is rendered directly from federal source data, no number is typed in by an editor. Component ratings, ADT, and condition category on this page are copied from the NBI record for this structure; no figure is typed in by an editor. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error. Data current as of 2024 NBI release. NBI condition categories reflect the latest reported inventory record, not a live safety, closure, or travel decision.