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.

When Clayton County's bridges were built

256 bridges with a recorded construction year, grouped by decade

bridges

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.

Source FHWA National Bridge Inventory (year built) As of 2024 NBI release

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 Poor
O'Brien County 264 4.9%
Guthrie County 263 36.9%
Clayton County (this page) 256 10.5%
Carroll County 249 6.8%
Cherokee County 248 29%
Poweshiek County 248 41.9%

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).

Similar average build year

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

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

Good-condition bridges (78)

GRAPE RD

Good

Over: DRY MILL CREEK

00000, Clayton, IA

Built 2011 Load: 39.9 t ADT: 79

DOLPHIN AVE

Good

Over: HICKORY CREEK

On Blackberry Rd, Clayton, IA

Built 2013 Load: 40.2 t ADT: 98

130TH ST

Good

Over: ROBERTS CREEK

0.5 miles E Gunder Rd, Clayton, IA

Built 2017 Load: 40.2 t ADT: 62

IA 128

Good

Over: DRY MILL CREEK

2.4 MI. E OF JCT. IA 13, Clayton, IA

Built 1979 Load: 40.7 t ADT: 1,420

IA 76

Good

Over: BLOODY RUN CREEK

0.2 MI. S OF N JCT. US 18, Clayton, IA

Built 1994 Load: 41.3 t ADT: 3,580

DOGWOOD AVE

Good

Over: STREAM

.1 M S 100th st, Clayton, IA

Built 2020 Load: 41.8 t ADT: 16

JAGUAR RD

Good

Over: ELK CREEK

000000000, Clayton, IA

Built 2009 Load: 42.8 t ADT: 579

MISSISSIPPI RD

Good

Over: SMALL

093022908, Clayton, IA

Built 1979 Load: 43.4 t ADT: 157

X 28

Good

Over: SMALL STREAM

T94 R4w S18, Clayton, IA

Built 2014 Load: 43.7 t ADT: 1,179

C 5X HARVESTER RD

Good

Over: BEAR CREEK

00000, Clayton, IA

Built 2011 Load: 43.7 t ADT: 108

B64 AGATE RD

Good

Over: STREAM

0.5 miles E Bugle Rd, Clayton, IA

Built 2018 Load: 45.0 t ADT: 295

US 52

Good

Over: MILL CREEK

0.5 MI. S OF S.R. C9Y, Clayton, IA

Built 1974 Load: 45.4 t ADT: 2,780

LACE AVE

Good

Over: SMALL STREAM

093032510, Clayton, IA

Built 2005 Load: 45.7 t ADT: 11

KEYSTONE RD

Good

Over: SNY MAGILL

094032202, Clayton, IA

Built 2017 Load: 46.3 t ADT: 62

BIG SPRING HATCH

Good

Over: STREAM

IN BIG SPRING FISH HATCHE, Clayton, IA

Built 1992 Load: 46.7 t ADT: 10

348TH ST

Good

Over: DRY RUN CREEK

020000501, Clayton, IA

Built 2006 Load: 48.2 t ADT: 30

172ND STREET

Good

Over: ROBERTS CREEK

094050703, Clayton, IA

Built 1993 Load: 48.2 t ADT: 26

230TH STREET

Good

Over: DRY MILL CREEK

093040801, Clayton, IA

Built 1993 Load: 49.8 t ADT: 44

165TH ST

Good

Over: SILVER CREEK

094050505, Clayton, IA

Built 1990 Load: 50.0 t ADT: 137

SPOOK CAVE RD

Good

Over: BLOODY RUN

095042204, Clayton, IA

Built 2004 Load: 50.0 t ADT: 113

CHERRYVALLEY RD

Good

Over: SMALL STREAM

091022760, Clayton, IA

Built 2012 Load: 54.1 t ADT: 104

IOWA AVE

Good

Over: ELK CREEK

T91 R4 S11, Clayton, IA

Built 2014 Load: 54.8 t ADT: 79

IA 13

Good

Over: ROBERTS CREEK

0.8 mi. S of S Jct IA 128, Clayton, IA

Built 1979 Load: 55.1 t ADT: 4,900

IRIS AVE

Good

Over: BLOODY RUN

095042404, Clayton, IA

Built 1996 Load: 58.0 t ADT: 59

CRYSTAL RD

Good

Over: STREAM

092062507, Clayton, IA

Built 1988 Load: 58.1 t ADT: 88

EVERGREEN RD

Good

Over: VOLGA RIVER

092052206, Clayton, IA

Built 1995 Load: 70.7 t ADT: 88

GRAIN RD

Good

Over: STREAM

T92 R4w Sec5, Clayton, IA

Built 2014 Load: 99.9 t ADT: 11

NATURE AVE

Good

Over: SMALL STREAM

T91N R2W Sec5, Clayton, IA

Built 2014 Load: 99.9 t ADT: 11

Read our methodology - how this data is sourced, computed, and verified.

Related

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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.