County profile · official public datasets

Clarke County, IA

168 public highway bridges tracked in the FHWA National Bridge Inventory: 27.4% rated Good, 41.1% Fair, 31.5% Poor.

168
Public bridges: 27.4%
Good condition: 31.5%
Poor condition

The verdict

According to the Federal Highway Administration's 2024 National Bridge Inventory.

Clarke County posts a higher-than-median Poor-condition share among rated counties in the state across mid-size county bridge inventory.

83rd
of 99 on Poor share: 31.5%
Poor-condition share: 168
public highway bridges: 1977
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.

Clarke County Bridge Snapshot

According to the Federal Highway Administration's 2024 National Bridge Inventory, Clarke County ranks #83 of 99 Iowa counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 31.5%). Clarke County, Iowa contains 168 public highway bridges. Roughly 27.4% are rated “Good,” 41.1% “Fair,” and 31.5% “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

168

Public highway bridges in Clarke County

Good condition

27.4%

46 of 168 rated 7-9

Fair condition

41.1%

69 of 168 rated 5-6

Poor condition

31.5%

53 of 168 rated 4 or below

In-state Poor-share rank

#83 of 99

Among Iowa counties with 5+ bridges, lower share ranks better

Condition distribution

Share of 168 NBI-tracked bridges by lowest applicable component rating.

Good

27.4% (46)

Fair

41.1% (69)

Poor

31.5% (53)

Clarke County's Poor-condition bridges carry 2,868 vehicle crossings a day

That is 2.6% of the county's reported daily bridge traffic on 31.5% of its bridges: Poor-condition structures carry less traffic than their share of the inventory. Each Poor bridge averages 54 crossings a day against 765 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 168 of 168 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.

42.3% of Clarke County's bridges have passed the 50-year mark

71 of the 168 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 27.4% 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 16% of the county's Poor-condition bridge traffic

FM over WALNUT CREEK, built 1976, carries 459 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 53-bridge count understates how much of the daily burden sits on a single crossing.

Share is of the 2,868 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.

1900s

14
1930s

1
1940s

2
1950s

11
1960s

27
1970s

34
1980s

32
1990s

6
2000s

15
2010s

20
2020s

6

What this shows Construction peaked in the 1970s, when 34 of the county's bridges still in the inventory were built, which is 20.2% of those with a recorded year. That cohort is now 45 to 54 years old in the 2024 inventory. Its average build year (1977) matches the Iowa average (1979).

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

The 5 Iowa counties nearest Clarke County in number of bridges, with their condition splits. Its 31.5% Poor share is the 5th-lowest of these 6. Its average build year of 1977 against a peer-group mean of 1977 is in line with the group.

Showing the 5 closest of 98 Iowa counties eligible for comparison.

Bridge inventory size and condition shares for Clarke County and the 5 Iowa counties closest to it in inventory size
County	Bridges	Good	Fair	Poor	Avg. built
Union County	169	30.2%	37.3%	32.5%	1978
Greene County	168	35.1%	50%	14.9%	1973
Clarke County (this page)	168	27.4%	41.1%	31.5%	1977
Mitchell County	167	47.3%	42.5%	10.2%	1980
Davis County	165	44.8%	29.7%	25.5%	1985
Hamilton County	165	39.4%	40%	20.6%	1970

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 Clarke 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 Clarke County, both outside Iowa so the neighborhoods are not the same-state size table above.

Similar inventory size

Nearest county inventories outside IA (168 bridges here).

Wilcox County, AL · 168 bridges
Kings County, CA · 168 bridges
Carroll County, GA · 168 bridges
Clayton County, GA · 168 bridges

Similar average build year

Nearest mean year-built outside IA (1977 here).

San Diego County, CA · avg 1977 · 1,632 bridges
King County, WA · avg 1977 · 1,238 bridges
Riverside County, CA · avg 1977 · 1,117 bridges
Shelby County, TN · avg 1977 · 1,077 bridges

Source: FHWA National Bridge Inventory, 2024 release. Peers floor at 10 bridges so stub inventories cannot own the match.

All 168 Good 46 Fair 69 Poor 53

Fair-condition bridges (69)

Sort:

Clarke County Bridge Snapshot

Condition distribution

Clarke County's Poor-condition bridges carry 2,868 vehicle crossings a day

42.3% of Clarke County's bridges have passed the 50-year mark

One structure carries 16% of the county's Poor-condition bridge traffic

How Clarke 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

Fair-condition bridges (69)

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