County profile · official public datasets

Clay County, IA

151 public highway bridges tracked in the FHWA National Bridge Inventory: 35.8% rated Good, 54.3% Fair, 9.9% Poor.

151
Public bridges: 35.8%
Good condition: 9.9%
Poor condition

The verdict

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

Clay County posts a top-quartile lowest Poor-condition share among rated counties in the state across mid-size county bridge inventory.

Top 19%
lowest Poor share in state: 9.9%
Poor-condition share: 151
public highway bridges: 1982
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.

Clay County Bridge Snapshot

According to the Federal Highway Administration's 2024 National Bridge Inventory, Clay County ranks #19 of 99 Iowa counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 9.9%). Clay County, Iowa contains 151 public highway bridges. Roughly 35.8% are rated “Good,” 54.3% “Fair,” and 9.9% “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 Clay County

Good condition

35.8%

54 of 151 rated 7-9

Fair condition

54.3%

82 of 151 rated 5-6

Poor condition

9.9%

15 of 151 rated 4 or below

In-state Poor-share rank

#19 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

35.8% (54)

Fair

54.3% (82)

Poor

9.9% (15)

Clay County's Poor-condition bridges carry 7,528 vehicle crossings a day

That is 7.2% of the county's reported daily bridge traffic on 9.9% of its bridges: Poor-condition structures carry less traffic than their share of the inventory. Each Poor bridge averages 502 crossings a day against 796 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 Clay 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 35.8% 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 34.2% of the county's Poor-condition bridge traffic

FM 340TH ST over LITTLE SIOUX RIVER, built 1963, carries 2,573 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 15-bridge count understates how much of the daily burden sits on a single crossing.

Share is of the 7,528 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.

1900s

3
1910s

4
1920s

2
1930s

4
1940s

1
1950s

3
1960s

22
1970s

28
1980s

12
1990s

28
2000s

29
2010s

11
2020s

4

What this shows Construction peaked in the 2000s, when 29 of the county's bridges still in the inventory were built, which is 19.2% of those with a recorded year. That cohort is now 15 to 24 years old in the 2024 inventory. Its average build year (1982) matches the Iowa average (1979).

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

The 5 Iowa counties nearest Clay County in number of bridges, with their condition splits. Its 9.9% Poor share is the 1st-lowest of these 6. Its average build year of 1982 against a peer-group mean of 1979 is in line with the group.

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

Bridge inventory size and condition shares for Clay 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
Louisa County	151	33.1%	50.3%	16.6%	1980
Clay County (this page)	151	35.8%	54.3%	9.9%	1982
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 Clay 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 Clay 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 (1982 here).

Oklahoma County, OK · avg 1982 · 1,216 bridges
Jackson County, MO · avg 1982 · 930 bridges
Milwaukee County, WI · avg 1982 · 893 bridges
Champaign County, IL · avg 1982 · 727 bridges

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

All 151 Good 54 Fair 82 Poor 15

Good-condition bridges (54)

Sort:

Clay County Bridge Snapshot

Condition distribution

Clay County's Poor-condition bridges carry 7,528 vehicle crossings a day

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

One structure carries 34.2% of the county's Poor-condition bridge traffic

How Clay 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

Good-condition bridges (54)

SR M22

PK 658(WANATA)

200TH AVE

390TH ST

160TH AVE

FM 430TH ST

340TH ST

140TH AVE

FM 240TH AVE

US 18

US 18

US 71

420TH ST

495TH ST

FM 170TH AVE

FM 240TH AVE

390TH ST

330TH ST

120TH AVE

400TH ST

460TH ST

390TH ST

370TH ST

150TH AVE

100TH AVE

FM 190TH AVE

IA 10

290TH ST

400TH ST

300TH ST

345TH ST

US 18 & 71

320TH AVE

FM 190TH AVE

N18 340TH AVE

FM 440TH ST

150TH AVE

FM 160TH AVE

N18 330TH AVE

310TH ST

310TH ST

1ST ST SOUTH

B63 (480TH ST)

300TH ST

430TH ST

340TH ST

300TH ST

330TH ST

LOCAL RD

270TH AVE

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