Total bridges
304
Public highway bridges in Rock County
County profile · official public datasets
Rock County, WI
304 public highway bridges tracked in the FHWA National Bridge Inventory: 61.2% rated Good, 35.2% Fair, 3.6% Poor.
- 304
- Public bridges
- 61.2%
- Good condition
- 3.6%
- Poor condition
The verdict
According to the Federal Highway Administration's 2024 National Bridge Inventory.
Rock County pairs a top-quartile lowest Poor-condition share among rated counties in the state with a newer average build year than the state inventory.
- Top 18%
- lowest Poor share in state
- 3.6%
- Poor-condition share
- 304
- public highway bridges
- 1994
- avg year built
Poor is an FHWA condition category from the lowest applicable component rating (4 or below), not a live crossing-safety or closure decision. Rankings cover counties with at least five public highway bridges.
Rock County Bridge Snapshot
According to the Federal Highway Administration's 2024 National Bridge Inventory, Rock County ranks #13 of 72 Wisconsin counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 3.6%). Rock County, Wisconsin contains 304 public highway bridges. Roughly 61.2% are rated “Good,” 35.2% “Fair,” and 3.6% “Poor.” Poor means the lowest applicable deck, superstructure, substructure, or culvert rating is 4 or below on the 0–9 NBI scale. It is a condition category, not a live safety or closure decision.
Responsible agencies inspect covered bridges on risk-based intervals under current NBIS rules and submit inventory data to FHWA annually. The list below shows every NBI-tracked bridge in the county. Use the “Sort by” controls to change the ordering, and click any row for its reported inspection date, traffic count, and condition fields.
Source: FHWA National Bridge Inventory. See methodology for full definitions.
Good condition
61.2%
186 of 304 rated 7-9
Fair condition
35.2%
107 of 304 rated 5-6
Poor condition
3.6%
11 of 304 rated 4 or below
In-state Poor-share rank
#13 of 72
Among Wisconsin counties with 5+ bridges, lower share ranks better
Condition distribution
Share of 304 NBI-tracked bridges by lowest applicable component rating.
Good 61.2% (186)
Fair 35.2% (107)
Poor 3.6% (11)
Rock County's Poor-condition bridges carry 23,461 vehicle crossings a day
That is 1% of the county's reported daily bridge traffic on 3.6% of its bridges: Poor-condition structures carry less traffic than their share of the inventory. Each Poor bridge averages 2,133 crossings a day against 9,870 for a Good-condition one. A Poor rating is a condition category, not a closure or a live safety judgement; it means the lowest applicable component rating is 4 or below.
Computed over the 304 of 304 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.
18.1% of Rock County's bridges have passed the 50-year mark
55 of the 304 bridges with a recorded construction year were built in 1974 or earlier. Age alone is not a defect: a well-maintained older bridge can rate Good, and 61.2% of this county's inventory does. Even so, this older cohort is the population from which future Poor ratings are drawn, which is why the age profile below matters alongside the condition split above.
Cutoff derives from the 2024 release year minus a 50-year design life. Source: FHWA National Bridge Inventory, 2024 release.
One structure carries 62.2% of the county's Poor-condition bridge traffic
USH 51-CENTER AVE over CNW RR, built 1982, carries 14,600 vehicles a day, the most of any Poor-rated structure here. The county's Poor-condition exposure is concentrated rather than evenly spread, so the 11-bridge count understates how much of the daily burden sits on a single crossing.
Share is of the 23,461 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.
When Rock County's bridges were built
304 bridges with a recorded construction year, grouped by decade
- pre-1900 1
Built before 1900
1 bridges
- 1910s 1
1910–1919
1 bridges
- 1920s 1
1920–1929
1 bridges
- 1930s 2
1930–1939
2 bridges
- 1940s 5
1940–1949
5 bridges
- 1950s 17
1950–1959
17 bridges
- 1960s 17
1960–1969
17 bridges
- 1970s
1970–1979
38 bridges
- 1980s
1980–1989
28 bridges
- 1990s
1990–1999
49 bridges
- 2000s
2000–2009
45 bridges
- 2010s
2010–2019
65 bridges
- 2020s
2020–2029
35 bridges
What this shows Construction peaked in the 2010s, when 65 of the county's bridges still in the inventory were built, which is 21.4% of those with a recorded year. That cohort is now 5 to 14 years old in the 2024 inventory. Its average build year is 1994, 10 years newer than the Wisconsin average of 1984.
How Rock County compares with Wisconsin's closest counties by inventory size
The 5 Wisconsin counties nearest Rock County in number of bridges, with their condition splits. Its 3.6% Poor share is the 2nd-lowest of these 6. Its average build year of 1994 against a peer-group mean of 1983 is 11 years newer.
Showing the 5 closest of 71 Wisconsin counties eligible for comparison.
| County | Bridges | Good | Fair | Poor | Avg. built |
|---|---|---|---|---|---|
| Barron County | 319 | 48.6% | 45.8% | 5.6% | 1978 |
| Rock County (this page) | 304 | 61.2% | 35.2% | 3.6% | 1994 |
| Richland County | 298 | 54% | 41.9% | 4% | 1986 |
| St. Croix County | 298 | 68.1% | 28.9% | 3% | 1986 |
| Clark County | 296 | 54.4% | 33.4% | 12.2% | 1983 |
| Outagamie County | 290 | 49.7% | 46.2% | 4.1% | 1982 |
Each share is of that county's own total tracked bridges; peers are the counties with 5 or more bridges whose inventory size is closest to Rock County's. Source: FHWA National Bridge Inventory, 2024 release.
Nationwide counties with similar inventory size or average build year
Two NBI-derived peer sets for Rock County, both outside Wisconsin so the neighborhoods are not the same-state size table above.
Similar inventory size
Nearest county inventories outside WI (304 bridges here).
- Coles County, IL · 304 bridges
- Knox County, IL · 304 bridges
- Marshall County, IA · 304 bridges
- Osage County, KS · 304 bridges
Similar average build year
Nearest mean year-built outside WI (1994 here).
- Denton County, TX · avg 1994 · 991 bridges
- St. Charles County, MO · avg 1994 · 417 bridges
- Pitt County, NC · avg 1994 · 228 bridges
- Columbus County, NC · avg 1994 · 226 bridges
Source: FHWA National Bridge Inventory, 2024 release. Peers floor at 10 bridges so stub inventories cannot own the match.
Poor-condition bridges (11)
LRD CLEOPHAS RD
PoorOver: RACCOON CREEK
0.7M E JCT CTH K, Rock, WI
Built 1918 Load: 6.8 t ADT: 82
LRD ORILEY RD
PoorOver: TURTLE CREEK
2.0M N JCT CTH X, Rock, WI
Built 1963 Load: 13.0 t ADT: 293
LRD LATHERS RD
PoorOver: TURTLE CREEK
0.1M N JCT CTH S, Rock, WI
Built 1887 Load: 14.6 t ADT: 474
LRD CALEDONIA RD
PoorOver: YAHARA RIVER
1.2M W JCT STH 184, Rock, WI
Built 1966 Load: 19.4 t ADT: 215
LRD N FOOTVILLE RD
PoorOver: BR STEVENS CREEK
1.5M S JCT CTH A, Rock, WI
Built 1980 Load: 19.4 t ADT: 23
USH 51-CENTER AVE
PoorOver: CNW RR
11.3M N JCT STH 81, Rock, WI
Built 1982 Load: 24.3 t ADT: 14,600
LRD MILTON SHOPIER
PoorOver: BR BLACKHAWK CREEK
0.4M S JCT CTH MM, Rock, WI
Built 1923 Load: 29.2 t ADT: 165
STH 213-4TH ST
PoorOver: ROCK RIVER
0.1M N JCT USH 51, Rock, WI
Built 1962 Load: 32.4 t ADT: 5,700
CTH N
PoorOver: OTTER CREEK
0.1M W JCT STH 26, Rock, WI
Built 1964 Load: 32.4 t ADT: 1,461
CTH J
PoorOver: LITTLE TURTLE CREEK
1.3M E JCT CTH P, Rock, WI
Built 1976 Load: 34.0 t ADT: 270
CTH KK
PoorOver: JOHNSTOWN CREEK
2.3M N JCT CTH M, Rock, WI
Built 1977 Load: 45.4 t ADT: 178
Read our methodology - how this data is sourced, computed, and verified.
Related
Data sourced from official public datasets. See our methodology for details. Retrieved and formatted by PlainBridges
Every figure on PlainBridges 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. NBI condition categories reflect the latest reported inventory record, not a live safety, closure, or travel decision.