Total bridges
151
Public highway bridges in Louisa County
County profile · official public datasets
Louisa County, IA
151 public highway bridges tracked in the FHWA National Bridge Inventory: 33.1% rated Good, 50.3% Fair, 16.6% Poor.
- 151
- Public bridges
- 33.1%
- Good condition
- 16.6%
- Poor condition
The verdict
According to the Federal Highway Administration's 2024 National Bridge Inventory.
Louisa County posts a better-than-median Poor-condition share among rated counties in the state across mid-size county bridge inventory.
- Top 40%
- lowest Poor share in state
- 16.6%
- Poor-condition share
- 151
- public highway bridges
- 1980
- 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.
Louisa County Bridge Snapshot
According to the Federal Highway Administration's 2024 National Bridge Inventory, Louisa County ranks #40 of 99 Iowa counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 16.6%). Louisa County, Iowa contains 151 public highway bridges. Roughly 33.1% are rated “Good,” 50.3% “Fair,” and 16.6% “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
33.1%
50 of 151 rated 7-9
Fair condition
50.3%
76 of 151 rated 5-6
Poor condition
16.6%
25 of 151 rated 4 or below
In-state Poor-share rank
#40 of 99
Among Iowa counties with 5+ bridges, lower share ranks better
Condition distribution
Share of 151 NBI-tracked bridges by lowest applicable component rating.
Good 33.1% (50)
Fair 50.3% (76)
Poor 16.6% (25)
Louisa County's Poor-condition bridges carry 4,008 vehicle crossings a day
That is 3.6% of the county's reported daily bridge traffic on 16.6% of its bridges: Poor-condition structures carry less traffic than their share of the inventory. Each Poor bridge averages 160 crossings a day against 619 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 151 of 151 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.
31.1% of Louisa County's bridges have passed the 50-year mark
47 of the 151 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 33.1% 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 21% of the county's Poor-condition bridge traffic
FM over SMALL STREAM, built 1969, carries 840 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 25-bridge count understates how much of the daily burden sits on a single crossing.
Share is of the 4,008 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.
When Louisa County's bridges were built
151 bridges with a recorded construction year, grouped by decade
- pre-1900 1
Built before 1900
1 bridges
- 1910s 1
1910–1919
1 bridges
- 1920s 5
1920–1929
5 bridges
- 1930s 3
1930–1939
3 bridges
- 1940s 2
1940–1949
2 bridges
- 1950s 12
1950–1959
12 bridges
- 1960s 15
1960–1969
15 bridges
- 1970s
1970–1979
26 bridges
- 1980s
1980–1989
42 bridges
- 1990s
1990–1999
19 bridges
- 2000s 6
2000–2009
6 bridges
- 2010s 10
2010–2019
10 bridges
- 2020s 9
2020–2029
9 bridges
What this shows Construction peaked in the 1980s, when 42 of the county's bridges still in the inventory were built, which is 27.8% of those with a recorded year. That cohort is now 35 to 44 years old in the 2024 inventory. Its average build year (1980) matches the Iowa average (1979).
How Louisa County compares with Iowa's closest counties by inventory size
The 5 Iowa counties nearest Louisa County in number of bridges, with their condition splits. Its 16.6% Poor share is the 2nd-lowest of these 6. Its average build year of 1980 against a peer-group mean of 1980 is in line with the group.
Showing the 5 closest of 98 Iowa counties eligible for comparison.
| County | Bridges | Good | Fair | Poor | Avg. built |
|---|---|---|---|---|---|
| Jefferson County | 157 | 43.9% | 37.6% | 18.5% | 1983 |
| Buena Vista County | 156 | 35.9% | 32.7% | 31.4% | 1979 |
| Van Buren County | 156 | 23.7% | 44.9% | 31.4% | 1975 |
| Clay County | 151 | 35.8% | 54.3% | 9.9% | 1982 |
| Louisa County (this page) | 151 | 33.1% | 50.3% | 16.6% | 1980 |
| Muscatine County | 144 | 34.7% | 43.8% | 21.5% | 1979 |
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 Louisa 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 Louisa County, both outside Iowa so the neighborhoods are not the same-state size table above.
Similar inventory size
Nearest county inventories outside IA (151 bridges here).
- Randolph County, AR · 151 bridges
- Pasco County, FL · 151 bridges
- St. Lucie County, FL · 151 bridges
- Hall County, GA · 151 bridges
Similar average build year
Nearest mean year-built outside IA (1980 here).
- Tulsa County, OK · avg 1980 · 1,135 bridges
- Miami-Dade County, FL · avg 1980 · 1,057 bridges
- Pulaski County, AR · avg 1980 · 721 bridges
- McLennan County, TX · avg 1980 · 714 bridges
Source: FHWA National Bridge Inventory, 2024 release. Peers floor at 10 bridges so stub inventories cannot own the match.
All bridges (151)
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.