County profile · official public datasets

Winnebago County, IA

55 public highway bridges tracked in the FHWA National Bridge Inventory: 30.9% rated Good, 36.4% Fair, 32.7% Poor.

55
Public bridges: 30.9%
Good condition: 32.7%
Poor condition

The verdict

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

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

87th
of 99 on Poor share: 32.7%
Poor-condition share: 55
public highway bridges: 1984
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.

Winnebago County Bridge Snapshot

According to the Federal Highway Administration's 2024 National Bridge Inventory, Winnebago County ranks #87 of 99 Iowa counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 32.7%). Winnebago County, Iowa contains 55 public highway bridges. Roughly 30.9% are rated “Good,” 36.4% “Fair,” and 32.7% “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

Public highway bridges in Winnebago County

Good condition

30.9%

17 of 55 rated 7-9

Fair condition

36.4%

20 of 55 rated 5-6

Poor condition

32.7%

18 of 55 rated 4 or below

In-state Poor-share rank

#87 of 99

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

Condition distribution

Share of 55 NBI-tracked bridges by lowest applicable component rating.

Good

30.9% (17)

Fair

36.4% (20)

Poor

32.7% (18)

Winnebago County's Poor-condition bridges carry 1,643 vehicle crossings a day

That is 6.1% of the county's reported daily bridge traffic on 32.7% of its bridges: Poor-condition structures carry less traffic than their share of the inventory. Each Poor bridge averages 91 crossings a day against 71 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 55 of 55 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.

29.1% of Winnebago County's bridges have passed the 50-year mark

16 of the 55 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 30.9% 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 57.1% of the county's Poor-condition bridge traffic

FM over BLUE EARTH RIVER, built 1924, carries 938 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 18-bridge count understates how much of the daily burden sits on a single crossing.

Share is of the 1,643 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.

1900s

1
1920s

2
1930s

1
1940s

2
1950s

3
1960s

5
1970s

10
1980s

7
1990s

4
2000s

7
2010s

11
2020s

2

What this shows Construction peaked in the 2010s, when 11 of the county's bridges still in the inventory were built, which is 20% of those with a recorded year. That cohort is now 5 to 14 years old in the 2024 inventory. Its average build year is 1984, 5 years newer than the Iowa average of 1979.

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

The 5 Iowa counties nearest Winnebago County in number of bridges, with their condition splits. Its 32.7% Poor share is the 6th-lowest of these 6. Its average build year of 1984 against a peer-group mean of 1973 is 11 years newer.

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

Bridge inventory size and condition shares for Winnebago County and the 5 Iowa counties closest to it in inventory size
County	Bridges	Good	Fair	Poor	Avg. built
Monroe County	130	26.2%	49.2%	24.6%	1977
Worth County	116	35.3%	48.3%	16.4%	1970
Humboldt County	87	36.8%	52.9%	10.3%	1965
Dickinson County	84	40.5%	41.7%	17.9%	1981
Emmet County	78	23.1%	60.3%	16.7%	1973
Winnebago County (this page)	55	30.9%	36.4%	32.7%	1984

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

Similar inventory size

Nearest county inventories outside IA (55 bridges here).

Park County, CO · 55 bridges
Dixie County, FL · 55 bridges
Logan County, KS · 55 bridges
Gallatin County, KY · 55 bridges

Similar average build year

Nearest mean year-built outside IA (1984 here).

Hennepin County, MN · avg 1984 · 936 bridges
Duval County, FL · avg 1984 · 831 bridges
El Paso County, CO · avg 1984 · 686 bridges
Bell County, TX · avg 1984 · 660 bridges

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

All 55 Good 17 Fair 20 Poor 18

All bridges (55)

Sort:

Winnebago County Bridge Snapshot

Condition distribution

Winnebago County's Poor-condition bridges carry 1,643 vehicle crossings a day

29.1% of Winnebago County's bridges have passed the 50-year mark

One structure carries 57.1% of the county's Poor-condition bridge traffic

How Winnebago 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

All bridges (55)

LOCAL

FM

460TH ST

US 69

US 69

FM

J ST

FM

FM

FM

SECOR AVE

LOCAL

IA 9

IA 9

FM

20TH AVE

US 69

10TH AVE

FM

US 69 & IA 9

A38 168TH AVE

160TH AVE

FM

FM

LOCAL

10TH AVE

A34 (420TH ST)

LOCAL

200TH AVE

LOCAL

350TH ST

440TH ST

LOCAL

30TH AVE

FM

LOCAL

140TH AVE

LOCAL

LOCAL

FM

LOCAL

135TH AVE

LOCAL

LOCAL

BROADWAY AVE

LOCAL

LOCAL

LOCAL

LOCAL

LOCAL

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