County profile · official public datasets

Union County, IA

169 public highway bridges tracked in the FHWA National Bridge Inventory: 30.2% rated Good, 37.3% Fair, 32.5% Poor.

169
Public bridges: 30.2%
Good condition: 32.5%
Poor condition

The verdict

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

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

86th
of 99 on Poor share: 32.5%
Poor-condition share: 169
public highway bridges: 1978
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.

Union County Bridge Snapshot

According to the Federal Highway Administration's 2024 National Bridge Inventory, Union County ranks #86 of 99 Iowa counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 32.5%). Union County, Iowa contains 169 public highway bridges. Roughly 30.2% are rated “Good,” 37.3% “Fair,” and 32.5% “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

169

Public highway bridges in Union County

Good condition

30.2%

51 of 169 rated 7-9

Fair condition

37.3%

63 of 169 rated 5-6

Poor condition

32.5%

55 of 169 rated 4 or below

In-state Poor-share rank

#86 of 99

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

Condition distribution

Share of 169 NBI-tracked bridges by lowest applicable component rating.

Good

30.2% (51)

Fair

37.3% (63)

Poor

32.5% (55)

Union County's Poor-condition bridges carry 4,179 vehicle crossings a day

That is 5.9% of the county's reported daily bridge traffic on 32.5% of its bridges: Poor-condition structures carry less traffic than their share of the inventory. Each Poor bridge averages 76 crossings a day against 276 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 169 of 169 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.

36.1% of Union County's bridges have passed the 50-year mark

61 of the 169 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 30.2% 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 20.9% of the county's Poor-condition bridge traffic

LINCOLN ST over HURLEY CREEK, built 1973, carries 875 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 55-bridge count understates how much of the daily burden sits on a single crossing.

Share is of the 4,179 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.

1900s

12
1930s

1
1940s

4
1950s

14
1960s

14
1970s

37
1980s

22
1990s

25
2000s

20
2010s

15
2020s

5

What this shows Construction peaked in the 1970s, when 37 of the county's bridges still in the inventory were built, which is 21.9% of those with a recorded year. That cohort is now 45 to 54 years old in the 2024 inventory. Its average build year (1978) matches the Iowa average (1979).

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

The 5 Iowa counties nearest Union County in number of bridges, with their condition splits. Its 32.5% Poor share is the 6th-lowest of these 6. Its average build year of 1978 against a peer-group mean of 1979 is in line with the group.

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

Bridge inventory size and condition shares for Union County and the 5 Iowa counties closest to it in inventory size
County	Bridges	Good	Fair	Poor	Avg. built
Henry County	173	41%	37.6%	21.4%	1982
Union County (this page)	169	30.2%	37.3%	32.5%	1978
Clarke County	168	27.4%	41.1%	31.5%	1977
Greene County	168	35.1%	50%	14.9%	1973
Mitchell County	167	47.3%	42.5%	10.2%	1980
Davis County	165	44.8%	29.7%	25.5%	1985

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

Similar inventory size

Nearest county inventories outside IA (169 bridges here).

Pike County, AL · 169 bridges
Laurens County, GA · 169 bridges
Cumberland County, IL · 169 bridges
Rooks County, KS · 169 bridges

Similar average build year

Nearest mean year-built outside IA (1978 here).

Orange County, CA · avg 1978 · 1,164 bridges
Sumner County, KS · avg 1978 · 659 bridges
Allen County, IN · avg 1978 · 613 bridges
Livingston County, IL · avg 1978 · 579 bridges

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

All 169 Good 51 Fair 63 Poor 55

Poor-condition bridges (55)

Sort:

Union County Bridge Snapshot

Condition distribution

Union County's Poor-condition bridges carry 4,179 vehicle crossings a day

36.1% of Union County's bridges have passed the 50-year mark

One structure carries 20.9% of the county's Poor-condition bridge traffic

How Union 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 (55)

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