County profile · official public datasets

Woodbury County, IA

455 public highway bridges tracked in the FHWA National Bridge Inventory: 39.3% rated Good, 39.6% Fair, 21.1% Poor.

455
Public bridges: 39.3%
Good condition: 21.1%
Poor condition

The verdict

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

Woodbury 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.

58th
of 99 on Poor share: 21.1%
Poor-condition share: 455
public highway bridges: 1985
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.

Woodbury County Bridge Snapshot

According to the Federal Highway Administration's 2024 National Bridge Inventory, Woodbury County ranks #58 of 99 Iowa counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 21.1%). Woodbury County, Iowa contains 455 public highway bridges. Roughly 39.3% are rated “Good,” 39.6% “Fair,” and 21.1% “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

455

Public highway bridges in Woodbury County

Good condition

39.3%

179 of 455 rated 7-9

Fair condition

39.6%

180 of 455 rated 5-6

Poor condition

21.1%

96 of 455 rated 4 or below

In-state Poor-share rank

#58 of 99

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

Condition distribution

Share of 455 NBI-tracked bridges by lowest applicable component rating.

Good

39.3% (179)

Fair

39.6% (180)

Poor

21.1% (96)

Woodbury County's Poor-condition bridges carry 45,786 vehicle crossings a day

That is 3.6% of the county's reported daily bridge traffic on 21.1% of its bridges: Poor-condition structures carry less traffic than their share of the inventory. Each Poor bridge averages 477 crossings a day against 2,710 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 455 of 455 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.

31% of Woodbury County's bridges have passed the 50-year mark

141 of the 455 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 39.3% 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 19.6% of the county's Poor-condition bridge traffic

6TH ST over FLOYD RIVER, built 1962, carries 8,957 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 96-bridge count understates how much of the daily burden sits on a single crossing.

Share is of the 45,786 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.

1900s

6
1910s

1
1920s

2
1930s

9
1940s

7
1950s

61
1960s

43
1970s

57
1980s

45
1990s

54
2000s

80
2010s

77
2020s

13

What this shows Construction peaked in the 2000s, when 80 of the county's bridges still in the inventory were built, which is 17.6% of those with a recorded year. That cohort is now 15 to 24 years old in the 2024 inventory. Its average build year is 1985, 6 years newer than the Iowa average of 1979.

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

The 5 Iowa counties nearest Woodbury County in number of bridges, with their condition splits. Its 21.1% Poor share is the 4th-lowest of these 6. Its average build year of 1985 against a peer-group mean of 1981 is in line with the group.

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

Bridge inventory size and condition shares for Woodbury County and the 5 Iowa counties closest to it in inventory size
County	Bridges	Good	Fair	Poor	Avg. built
Linn County	506	46.4%	47.2%	6.3%	1987
Black Hawk County	489	52.8%	40.7%	6.5%	1983
Woodbury County (this page)	455	39.3%	39.6%	21.1%	1985
Sioux County	449	62.4%	34.7%	2.9%	1982
Plymouth County	432	52.1%	26.4%	21.5%	1974
Jasper County	382	38.5%	32.5%	29.1%	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 Woodbury 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 Woodbury County, both outside Iowa so the neighborhoods are not the same-state size table above.

Similar inventory size

Nearest county inventories outside IA (455 bridges here).

Hunt County, TX · 456 bridges
Hamilton County, IN · 454 bridges
Forsyth County, NC · 454 bridges
Somerset County, PA · 454 bridges

Similar average build year

Nearest mean year-built outside IA (1985 here).

Hillsborough County, FL · avg 1985 · 840 bridges
Lancaster County, NE · avg 1985 · 661 bridges
Nueces County, TX · avg 1985 · 528 bridges
Grayson County, TX · avg 1985 · 513 bridges

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

All 455 Good 179 Fair 180 Poor 96

Fair-condition bridges (180)

Sort:

Woodbury County Bridge Snapshot

Condition distribution

Woodbury County's Poor-condition bridges carry 45,786 vehicle crossings a day

31% of Woodbury County's bridges have passed the 50-year mark

One structure carries 19.6% of the county's Poor-condition bridge traffic

How Woodbury 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

Fair-condition bridges (180)

28TH ST

LOCAL

COUNTRY CLUB

LOCAL

LOCAL

120TH ST

GARNER AVE

LOCAL

HAMILTON BLVD

IA 141

LOCAL

STORY AVE

LOCAL

LOCAL

NB IA 12

LOCAL

LOCAL

WAR EAGLE DRIVE

LOCAL

LOCAL

LOCAL

LOCAL

LOCAL

FM

FM

FM

FM

SB IA 376

FM

LOCAL

MILITARY RD

FM

IA 141

ELM ST

LOCAL

SB IA 12

RAMP IA 12

US 20 EB

US 20 EB

IA 376 NB

IA 141

D51 (260TH ST)

I 29 NB

I 29 SB

I 29 NB

I 29 SB

I 29 SB

I 29 SB

WESLEY PKWY

US 20 WB

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