County profile · official public datasets

Grundy County, IA

289 public highway bridges tracked in the FHWA National Bridge Inventory: 42.6% rated Good, 32.9% Fair, 24.6% Poor.

289
Public bridges: 42.6%
Good condition: 24.6%
Poor condition

The verdict

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

Grundy County posts a higher-than-median Poor-condition share among rated counties in the state across mid-size county bridge inventory.

65th
of 99 on Poor share: 24.6%
Poor-condition share: 289
public highway bridges: 1983
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.

Grundy County Bridge Snapshot

According to the Federal Highway Administration's 2024 National Bridge Inventory, Grundy County ranks #65 of 99 Iowa counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 24.6%). Grundy County, Iowa contains 289 public highway bridges. Roughly 42.6% are rated “Good,” 32.9% “Fair,” and 24.6% “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

289

Public highway bridges in Grundy County

Good condition

42.6%

123 of 289 rated 7-9

Fair condition

32.9%

95 of 289 rated 5-6

Poor condition

24.6%

71 of 289 rated 4 or below

In-state Poor-share rank

#65 of 99

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

Condition distribution

Share of 289 NBI-tracked bridges by lowest applicable component rating.

Good

42.6% (123)

Fair

32.9% (95)

Poor

24.6% (71)

Grundy County's Poor-condition bridges carry 15,133 vehicle crossings a day

That is 7.1% of the county's reported daily bridge traffic on 24.6% of its bridges: Poor-condition structures carry less traffic than their share of the inventory. Each Poor bridge averages 213 crossings a day against 1,229 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 289 of 289 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.

32.5% of Grundy County's bridges have passed the 50-year mark

94 of the 289 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 42.6% 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 21.3% of the county's Poor-condition bridge traffic

IA 14 over BLACK HAWK CREEK, built 1931, carries 3,230 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 71-bridge count understates how much of the daily burden sits on a single crossing.

Share is of the 15,133 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.

1900s

2
1910s

3
1920s

1
1930s

2
1940s

5
1950s

32
1960s

25
1970s

69
1980s

38
1990s

32
2000s

47
2010s

25
2020s

8

What this shows Construction peaked in the 1970s, when 69 of the county's bridges still in the inventory were built, which is 23.9% of those with a recorded year. That cohort is now 45 to 54 years old in the 2024 inventory. Its average build year (1983) matches the Iowa average (1979).

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

The 5 Iowa counties nearest Grundy County in number of bridges, with their condition splits. Its 24.6% Poor share is the 5th-lowest of these 6. Its average build year of 1983 against a peer-group mean of 1978 is 5 years newer.

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

Bridge inventory size and condition shares for Grundy County and the 5 Iowa counties closest to it in inventory size
County	Bridges	Good	Fair	Poor	Avg. built
Story County	296	33.1%	53%	13.9%	1968
Cass County	295	25.4%	41%	33.6%	1976
Delaware County	293	39.2%	53.9%	6.8%	1981
Scott County	291	34.7%	55%	10.3%	1980
Butler County	289	58.1%	26.6%	15.2%	1985
Grundy County (this page)	289	42.6%	32.9%	24.6%	1983

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

Similar inventory size

Nearest county inventories outside IA (289 bridges here).

Union County, AR · 289 bridges
McKinley County, NM · 289 bridges
Knox County, IN · 290 bridges
Putnam County, IN · 290 bridges

Similar average build year

Nearest mean year-built outside IA (1983 here).

Dallas County, TX · avg 1983 · 3,230 bridges
Bexar County, TX · avg 1983 · 2,342 bridges
Sedgwick County, KS · avg 1983 · 1,333 bridges
Will County, IL · avg 1983 · 649 bridges

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

All 289 Good 123 Fair 95 Poor 71

Good-condition bridges (123)

Sort:

Grundy County Bridge Snapshot

Condition distribution

Grundy County's Poor-condition bridges carry 15,133 vehicle crossings a day

32.5% of Grundy County's bridges have passed the 50-year mark

One structure carries 21.3% of the county's Poor-condition bridge traffic

How Grundy 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 (123)

US 20 WB ON RAMP

US 20 EB OFF RAMP

VISTA AVE

250TH ST

LOCAL

LOCAL ROAD

LOCAL

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FM

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IA 175

H AVE

T37 M AVE

300TH ST

X AVE

230TH ST

R AVE

180TH ST

SR D35

G AVE

FM

KING AVE

LOCAL

LOCAL

LOCAL

LOCAL

175TH ST

FM

LOCAL

FM

LOCAL

LOCAL RD

LOCAL

LOCAL ROAD

LOCAL

LOCAL

LOCAL

FM

LOCAL

LOCAL

LOCAL

A AVE

FM

E AVE

260TH ST

C AVE

T13 D AVE

250TH ST

K AVE

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