County profile · official public datasets

Clinton County, IA

372 public highway bridges tracked in the FHWA National Bridge Inventory: 66.7% rated Good, 30.4% Fair, 3% Poor.

372
Public bridges: 66.7%
Good condition: 3%
Poor condition

The verdict

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

Clinton County pairs a top-5% lowest Poor-condition share among rated counties in the state with a newer average build year than the state inventory.

Top 2%
lowest Poor share in state: 3%
Poor-condition share: 372
public highway bridges: 1986
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.

Clinton County Bridge Snapshot

According to the Federal Highway Administration's 2024 National Bridge Inventory, Clinton County ranks #2 of 99 Iowa counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 3%). Clinton County, Iowa contains 372 public highway bridges. Roughly 66.7% are rated “Good,” 30.4% “Fair,” and 3% “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

372

Public highway bridges in Clinton County

Good condition

66.7%

248 of 372 rated 7-9

Fair condition

30.4%

113 of 372 rated 5-6

Poor condition

11 of 372 rated 4 or below

In-state Poor-share rank

#2 of 99

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

Condition distribution

Share of 372 NBI-tracked bridges by lowest applicable component rating.

Good

66.7% (248)

Fair

30.4% (113)

Poor

3% (11)

Clinton County's Poor-condition bridges carry 4,275 vehicle crossings a day

That is 0.9% of the county's reported daily bridge traffic on 3% of its bridges: Poor-condition structures carry less traffic than their share of the inventory. Each Poor bridge averages 389 crossings a day against 845 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 372 of 372 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.

28.8% of Clinton County's bridges have passed the 50-year mark

107 of the 372 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 66.7% 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 33% of the county's Poor-condition bridge traffic

HARTS MILL RD over MILL CREEK, built 1970, carries 1,410 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 11-bridge count understates how much of the daily burden sits on a single crossing.

Share is of the 4,275 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.

1900s

1
1910s

2
1920s

8
1930s

3
1940s

2
1950s

25
1960s

36
1970s

57
1980s

52
1990s

69
2000s

60
2010s

42
2020s

15

What this shows Construction peaked in the 1990s, when 69 of the county's bridges still in the inventory were built, which is 18.5% of those with a recorded year. That cohort is now 25 to 34 years old in the 2024 inventory. Its average build year is 1986, 7 years newer than the Iowa average of 1979.

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

The 5 Iowa counties nearest Clinton County in number of bridges, with their condition splits. Its 3% Poor share is the 1st-lowest of these 6. Its average build year of 1986 against a peer-group mean of 1981 is 5 years newer.

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

Bridge inventory size and condition shares for Clinton County and the 5 Iowa counties closest to it in inventory size
County	Bridges	Good	Fair	Poor	Avg. built
Jasper County	382	38.5%	32.5%	29.1%	1977
Benton County	374	34.2%	42.8%	23%	1984
Johnson County	372	39.5%	50.3%	10.2%	1979
Clinton County (this page)	372	66.7%	30.4%	3%	1986
Fayette County	362	35.1%	40.3%	24.6%	1974
Dubuque County	346	50.6%	40.8%	8.7%	1989

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

Similar inventory size

Nearest county inventories outside IA (372 bridges here).

Harper County, KS · 372 bridges
Harvey County, KS · 372 bridges
Wharton County, TX · 372 bridges
Solano County, CA · 373 bridges

Similar average build year

Nearest mean year-built outside IA (1986 here).

El Paso County, TX · avg 1986 · 783 bridges
Caddo County, LA · avg 1986 · 682 bridges
Weld County, CO · avg 1986 · 614 bridges
Canadian County, OK · avg 1986 · 493 bridges

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

All 372 Good 248 Fair 113 Poor 11

Good-condition bridges (248)

Sort:

Clinton County Bridge Snapshot

Condition distribution

Clinton County's Poor-condition bridges carry 4,275 vehicle crossings a day

28.8% of Clinton County's bridges have passed the 50-year mark

One structure carries 33% of the county's Poor-condition bridge traffic

How Clinton 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 (248)

262ND ST

OLD US 61

MAIN ST OLD US 61

US 67

190TH STREET

160TH ST

SB US 61

170TH AVE.

160TH AVE

150TH ST.

110TH ST.

432ND AVENUE

150TH ST.

425TH AVE

390TH AVE

US 61

US 61

US 61

US 61

2ND AVE RD

280TH ST

230TH AVENUE

372ND AVE

NB US 61

180TH AVE.

US 30

US 30

105TH ST.

240TH ST

270TH AVE

235TH AVE

135TH STREET

308TH AVE

220TH AVE

240TH AVE

200TH AVENUE

135TH ST.

215TH AVE

E63 190TH ST

130TH AVE.

210TH ST.

NB US 61

CO RD Z 36

278TH ST

NB US 61

SB US 61

NB US 61

NB US 61

W DEER CK RD

SEVEN DAY RD

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