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.

Total bridges

151

Public highway bridges in Louisa County

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.

pre-1900

1
1910s

1
1920s

5
1930s

3
1940s

2
1950s

12
1960s

15
1970s

26
1980s

42
1990s

19
2000s

6
2010s

10
2020s

9

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.

Bridge inventory size and condition shares for Louisa County and the 5 Iowa counties closest to it in inventory size
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 151 Good 50 Fair 76 Poor 25

All bridges (151)

Sort:

Louisa County Bridge Snapshot

Condition distribution

Louisa County's Poor-condition bridges carry 4,008 vehicle crossings a day

31.1% of Louisa County's bridges have passed the 50-year mark

One structure carries 21% of the county's Poor-condition bridge traffic

How Louisa County compares with Iowa's closest counties by inventory size

Nationwide counties with similar inventory size or average build year

Similar inventory size

Similar average build year

All bridges (151)

FM

IA 78

FM

LOCAL

LEVEE

FM

WALNUT ST

FM

LOCAL

LOCAL

LOCAL

FM

FM

LOCAL

LOCAL

FM

FM

LOCAL

FM

LOCAL

FM

FM

FM

LOCAL

LOCAL

LOCAL

FM

LOCAL

LOCAL

LOCAL

LOCAL

LOCAL

FM

US 61

LOCAL

IA 92

IA 92

US 61

X 99

LOCAL

LOCAL

LOCAL

LOCAL

LOCAL

LOCAL

FM

FM

60TH ST

LOCAL

CO RD H22

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