County profile · official public datasets

Benton County, IA

374 public highway bridges tracked in the FHWA National Bridge Inventory: 34.2% rated Good, 42.8% Fair, 23% Poor.

374
Public bridges: 34.2%
Good condition: 23%
Poor condition

The verdict

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

Benton 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.

64th
of 99 on Poor share: 23%
Poor-condition share: 374
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.

Benton County Bridge Snapshot

According to the Federal Highway Administration's 2024 National Bridge Inventory, Benton County ranks #64 of 99 Iowa counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 23%). Benton County, Iowa contains 374 public highway bridges. Roughly 34.2% are rated “Good,” 42.8% “Fair,” and 23% “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

374

Public highway bridges in Benton County

Good condition

34.2%

128 of 374 rated 7-9

Fair condition

42.8%

160 of 374 rated 5-6

Poor condition

23%

86 of 374 rated 4 or below

In-state Poor-share rank

#64 of 99

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

Condition distribution

Share of 374 NBI-tracked bridges by lowest applicable component rating.

Good

34.2% (128)

Fair

42.8% (160)

Poor

23% (86)

Benton County's Poor-condition bridges carry 35,803 vehicle crossings a day

That is 14.2% of the county's reported daily bridge traffic on 23% of its bridges: Poor-condition structures carry less traffic than their share of the inventory. Each Poor bridge averages 416 crossings a day against 956 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 374 of 374 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.

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

109 of the 374 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 34.2% 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 21.2% of the county's Poor-condition bridge traffic

US 30 over PRAIRIE CREEK, built 1950, carries 7,600 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 86-bridge count understates how much of the daily burden sits on a single crossing.

Share is of the 35,803 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.

1900s

7
1920s

3
1940s

9
1950s

32
1960s

25
1970s

63
1980s

84
1990s

75
2000s

34
2010s

28
2020s

14

What this shows Construction peaked in the 1980s, when 84 of the county's bridges still in the inventory were built, which is 22.5% of those with a recorded year. That cohort is now 35 to 44 years old in the 2024 inventory. Its average build year is 1984, 5 years newer than the Iowa average of 1979.

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

The 5 Iowa counties nearest Benton County in number of bridges, with their condition splits. Its 23% Poor share is the 4th-lowest of these 6. Its average build year of 1984 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 Benton 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 (this page)	374	34.2%	42.8%	23%	1984
Clinton County	372	66.7%	30.4%	3%	1986
Johnson County	372	39.5%	50.3%	10.2%	1979
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 Benton 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 Benton County, both outside Iowa so the neighborhoods are not the same-state size table above.

Similar inventory size

Nearest county inventories outside IA (374 bridges here).

Baltimore city County, MD · 374 bridges
Rankin County, MS · 374 bridges
Cape Girardeau County, MO · 374 bridges
Monroe County, WI · 374 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 374 Good 128 Fair 160 Poor 86

Poor-condition bridges (86)

Sort:

Benton County Bridge Snapshot

Condition distribution

Benton County's Poor-condition bridges carry 35,803 vehicle crossings a day

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

One structure carries 21.2% of the county's Poor-condition bridge traffic

How Benton 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

Poor-condition bridges (86)

US 30

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