County profile · official public datasets

Calhoun County, IA

197 public highway bridges tracked in the FHWA National Bridge Inventory: 24.4% rated Good, 50.3% Fair, 25.4% Poor.

197
Public bridges: 24.4%
Good condition: 25.4%
Poor condition

The verdict

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

Calhoun County pairs a higher-than-median Poor-condition share among rated counties in the state with an older average build year than the state inventory.

72nd
of 99 on Poor share: 25.4%
Poor-condition share: 197
public highway bridges: 1971
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.

Calhoun County Bridge Snapshot

According to the Federal Highway Administration's 2024 National Bridge Inventory, Calhoun County ranks #72 of 99 Iowa counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 25.4%). Calhoun County, Iowa contains 197 public highway bridges. Roughly 24.4% are rated “Good,” 50.3% “Fair,” and 25.4% “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

197

Public highway bridges in Calhoun County

Good condition

24.4%

48 of 197 rated 7-9

Fair condition

50.3%

99 of 197 rated 5-6

Poor condition

25.4%

50 of 197 rated 4 or below

In-state Poor-share rank

#72 of 99

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

Condition distribution

Share of 197 NBI-tracked bridges by lowest applicable component rating.

Good

24.4% (48)

Fair

50.3% (99)

Poor

25.4% (50)

Calhoun County's Poor-condition bridges carry 3,596 vehicle crossings a day

That is 5.7% of the county's reported daily bridge traffic on 25.4% of its bridges: Poor-condition structures carry less traffic than their share of the inventory. Each Poor bridge averages 72 crossings a day against 786 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 197 of 197 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.

48.2% of Calhoun County's bridges have passed the 50-year mark

95 of the 197 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 24.4% 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 10% of the county's Poor-condition bridge traffic

FM over LAKE CR., built 1978, carries 359 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 50-bridge count understates how much of the daily burden sits on a single crossing.

Share is of the 3,596 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.

1900s

16
1910s

2
1920s

4
1930s

8
1940s

1
1950s

8
1960s

17
1970s

56
1980s

37
1990s

29
2000s

9
2010s

7
2020s

3

What this shows Construction peaked in the 1970s, when 56 of the county's bridges still in the inventory were built, which is 28.4% of those with a recorded year. That cohort is now 45 to 54 years old in the 2024 inventory. Its average build year is 1971, 8 years older than the Iowa average of 1979.

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

The 5 Iowa counties nearest Calhoun County in number of bridges, with their condition splits. Its 25.4% Poor share is the 3rd-lowest of these 6. Its average build year of 1971 against a peer-group mean of 1975 is in line with the group.

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

Bridge inventory size and condition shares for Calhoun County and the 5 Iowa counties closest to it in inventory size
County	Bridges	Good	Fair	Poor	Avg. built
Dallas County	199	44.7%	46.2%	9%	1978
Allamakee County	197	31.5%	59.4%	9.1%	1975
Decatur County	197	18.3%	41.1%	40.6%	1972
Calhoun County (this page)	197	24.4%	50.3%	25.4%	1971
Page County	196	24%	43.9%	32.1%	1975
Lucas County	195	32.3%	34.4%	33.3%	1977

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

Similar inventory size

Nearest county inventories outside IA (197 bridges here).

Crawford County, IL · 197 bridges
Fountain County, IN · 197 bridges
Warrick County, IN · 197 bridges
Atchison County, KS · 197 bridges

Similar average build year

Nearest mean year-built outside IA (1971 here).

Wayne County, MI · avg 1971 · 1,026 bridges
Baltimore County, MD · avg 1971 · 783 bridges
Washington County, PA · avg 1971 · 655 bridges
Linn County, OR · avg 1971 · 566 bridges

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

All 197 Good 48 Fair 99 Poor 50

Good-condition bridges (48)

Sort:

Calhoun County Bridge Snapshot

Condition distribution

Calhoun County's Poor-condition bridges carry 3,596 vehicle crossings a day

48.2% of Calhoun County's bridges have passed the 50-year mark

One structure carries 10% of the county's Poor-condition bridge traffic

How Calhoun 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 (48)

US 20

LOCAL

FM

LOCAL

380TH ST

D68 390TH ST

HARRIS AVE

US 20 EB

US 20 WB

270TH ST

FM

FM

LOCAL

US 20

US 20 WB

US 20 EB

US 20

LOCAL

LOCAL

FM

D36 270TH ST

LOCAL

FM

LOCAL

LOCAL

LOCAL

FM

LOCAL

FM

FM

FM

FM

INWOOD

FM

FM

FM

IA 4

FM

LOCAL

LOCAL

LOCAL

FM

IA 7

LOCAL

FM

IA 4

LOCAL

LOCAL

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