County profile · official public datasets

Marion County, IA

217 public highway bridges tracked in the FHWA National Bridge Inventory: 38.7% rated Good, 48.8% Fair, 12.4% Poor.

217
Public bridges: 38.7%
Good condition: 12.4%
Poor condition

The verdict

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

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

Top 26%
lowest Poor share in state: 12.4%
Poor-condition share: 217
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.

Marion County Bridge Snapshot

According to the Federal Highway Administration's 2024 National Bridge Inventory, Marion County ranks #26 of 99 Iowa counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 12.4%). Marion County, Iowa contains 217 public highway bridges. Roughly 38.7% are rated “Good,” 48.8% “Fair,” and 12.4% “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

217

Public highway bridges in Marion County

Good condition

38.7%

84 of 217 rated 7-9

Fair condition

48.8%

106 of 217 rated 5-6

Poor condition

12.4%

27 of 217 rated 4 or below

In-state Poor-share rank

#26 of 99

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

Condition distribution

Share of 217 NBI-tracked bridges by lowest applicable component rating.

Good

38.7% (84)

Fair

48.8% (106)

Poor

12.4% (27)

Marion County's Poor-condition bridges carry 9,992 vehicle crossings a day

That is 5.5% of the county's reported daily bridge traffic on 12.6% of its bridges: Poor-condition structures carry less traffic than their share of the inventory. Each Poor bridge averages 370 crossings a day against 893 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 214 of 217 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.

31.3% of Marion County's bridges have passed the 50-year mark

68 of the 217 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 38.7% 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 26.4% of the county's Poor-condition bridge traffic

FM over ENGLISH CREEK, built 1975, carries 2,640 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 27-bridge count understates how much of the daily burden sits on a single crossing.

Share is of the 9,992 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.

pre-1900

1
1900s

1
1910s

1
1920s

5
1940s

4
1950s

17
1960s

34
1970s

38
1980s

26
1990s

23
2000s

26
2010s

35
2020s

6

What this shows Construction peaked in the 1970s, when 38 of the county's bridges still in the inventory were built, which is 17.5% of those with a recorded year. That cohort is now 45 to 54 years old in the 2024 inventory. Its average build year is 1984, 5 years newer than the Iowa average of 1979.

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

The 5 Iowa counties nearest Marion County in number of bridges, with their condition splits. Its 12.4% Poor share is the 1st-lowest of these 6. Its average build year of 1984 against a peer-group mean of 1976 is 8 years newer.

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

Bridge inventory size and condition shares for Marion County and the 5 Iowa counties closest to it in inventory size
County	Bridges	Good	Fair	Poor	Avg. built
Taylor County	220	24.5%	37.7%	37.7%	1973
Harrison County	217	24.9%	56.2%	18.9%	1969
Ringgold County	217	25.3%	31.3%	43.3%	1971
Marion County (this page)	217	38.7%	48.8%	12.4%	1984
Lee County	214	44.9%	41.6%	13.6%	1981
Floyd County	213	49.8%	35.7%	14.6%	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 Marion 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 Marion County, both outside Iowa so the neighborhoods are not the same-state size table above.

Similar inventory size

Nearest county inventories outside IA (217 bridges here).

Sullivan County, IN · 217 bridges
Elko County, NV · 217 bridges
Portage County, OH · 217 bridges
Warren County, PA · 217 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 217 Good 84 Fair 106 Poor 27

Poor-condition bridges (27)

Sort:

Marion County Bridge Snapshot

Condition distribution

Marion County's Poor-condition bridges carry 9,992 vehicle crossings a day

31.3% of Marion County's bridges have passed the 50-year mark

One structure carries 26.4% of the county's Poor-condition bridge traffic

How Marion 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 (27)

FM

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OLD IOWA 92

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