County profile · official public datasets

Clayton County, IA

256 public highway bridges tracked in the FHWA National Bridge Inventory: 30.5% rated Good, 59% Fair, 10.5% Poor.

256
Public bridges: 30.5%
Good condition: 10.5%
Poor condition

The verdict

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

Clayton County pairs a top-quartile lowest Poor-condition share among rated counties in the state with an older average build year than the state inventory.

Top 24%
lowest Poor share in state: 10.5%
Poor-condition share: 256
public highway bridges: 1964
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.

Clayton County Bridge Snapshot

According to the Federal Highway Administration's 2024 National Bridge Inventory, Clayton County ranks #24 of 99 Iowa counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 10.5%). Clayton County, Iowa contains 256 public highway bridges. Roughly 30.5% are rated “Good,” 59% “Fair,” and 10.5% “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

256

Public highway bridges in Clayton County

Good condition

30.5%

78 of 256 rated 7-9

Fair condition

59%

151 of 256 rated 5-6

Poor condition

10.5%

27 of 256 rated 4 or below

In-state Poor-share rank

#24 of 99

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

Condition distribution

Share of 256 NBI-tracked bridges by lowest applicable component rating.

Good

30.5% (78)

Fair

59% (151)

Poor

10.5% (27)

Clayton County's Poor-condition bridges carry 6,478 vehicle crossings a day

That is 5.8% of the county's reported daily bridge traffic on 10.5% of its bridges: Poor-condition structures carry less traffic than their share of the inventory. Each Poor bridge averages 240 crossings a day against 513 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 256 of 256 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.

57.4% of Clayton County's bridges have passed the 50-year mark

147 of the 256 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 30.5% 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 73.4% of the county's Poor-condition bridge traffic

BRIDGE ST over TURKEY RIVER, built 1889, carries 4,755 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 27-bridge count understates how much of the daily burden sits on a single crossing.

Share is of the 6,478 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.

pre-1900

1
1900s

8
1910s

18
1920s

22
1930s

12
1940s

13
1950s

52
1960s

11
1970s

34
1980s

28
1990s

14
2000s

17
2010s

21
2020s

5

What this shows Construction peaked in the 1950s, when 52 of the county's bridges still in the inventory were built, which is 20.3% of those with a recorded year. That cohort is now 65 to 74 years old in the 2024 inventory. Its average build year is 1964, 15 years older than the Iowa average of 1979.

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

The 5 Iowa counties nearest Clayton County in number of bridges, with their condition splits. Its 10.5% Poor share is the 3rd-lowest of these 6. Its average build year of 1964 against a peer-group mean of 1974 is 10 years older.

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

Bridge inventory size and condition shares for Clayton County and the 5 Iowa counties closest to it in inventory size
County	Bridges	Good	Fair	Poor	Avg. built
O'Brien County	264	51.9%	43.2%	4.9%	1976
Guthrie County	263	24%	39.2%	36.9%	1976
Clayton County (this page)	256	30.5%	59%	10.5%	1964
Carroll County	249	48.6%	44.6%	6.8%	1977
Cherokee County	248	34.3%	36.7%	29%	1968
Poweshiek County	248	25%	33.1%	41.9%	1974

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

Similar inventory size

Nearest county inventories outside IA (256 bridges here).

Brown County, KS · 256 bridges
Chemung County, NY · 256 bridges
Chenango County, NY · 256 bridges
Essex County, NY · 256 bridges

Similar average build year

Nearest mean year-built outside IA (1964 here).

Bergen County, NJ · avg 1964 · 577 bridges
Morris County, NJ · avg 1964 · 508 bridges
Baltimore city County, MD · avg 1964 · 374 bridges
Ross County, OH · avg 1964 · 356 bridges

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

All 256 Good 78 Fair 151 Poor 27

Poor-condition bridges (27)

Sort:

Clayton County Bridge Snapshot

Condition distribution

Clayton County's Poor-condition bridges carry 6,478 vehicle crossings a day

57.4% of Clayton County's bridges have passed the 50-year mark

One structure carries 73.4% of the county's Poor-condition bridge traffic

How Clayton 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

Poor-condition bridges (27)

BRIDGE ST

6TH ST

B60-IVORY RD

A AVE

300TH ST

172ND ST

JUNE AVE

295TH ST

HORNET RD

GLACIER RD

MAIN ST-FOX AVE

HENNEPIN RD

ACORN RD

155TH ST

KEYSTONE RD

OAK ST

CRYSTAL RD

310TH ST

300TH ST

MESQUITE RD

BIXBY RD

BUCK CREEK RD

KAHLE AVE

FLEETWOOD RD

DRUMLIN RD

265TH ST

LANTERN AVE

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