County profile · official public datasets

Harrison County, IA

217 public highway bridges tracked in the FHWA National Bridge Inventory: 24.9% rated Good, 56.2% Fair, 18.9% Poor.

217
Public bridges: 24.9%
Good condition: 18.9%
Poor condition

The verdict

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

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

Top 49%
lowest Poor share in state: 18.9%
Poor-condition share: 217
public highway bridges: 1969
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.

Harrison County Bridge Snapshot

According to the Federal Highway Administration's 2024 National Bridge Inventory, Harrison County ranks #49 of 99 Iowa counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 18.9%). Harrison County, Iowa contains 217 public highway bridges. Roughly 24.9% are rated “Good,” 56.2% “Fair,” and 18.9% “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 Harrison County

Good condition

24.9%

54 of 217 rated 7-9

Fair condition

56.2%

122 of 217 rated 5-6

Poor condition

18.9%

41 of 217 rated 4 or below

In-state Poor-share rank

#49 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

24.9% (54)

Fair

56.2% (122)

Poor

18.9% (41)

Harrison County's Poor-condition bridges carry 2,479 vehicle crossings a day

That is 0.8% of the county's reported daily bridge traffic on 18.9% of its bridges: Poor-condition structures carry less traffic than their share of the inventory. Each Poor bridge averages 60 crossings a day against 997 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 217 of 217 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.

60.4% of Harrison County's bridges have passed the 50-year mark

131 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 24.9% 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 19.7% of the county's Poor-condition bridge traffic

AUSTIN AVE over STREAM, built 1936, carries 488 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 41-bridge count understates how much of the daily burden sits on a single crossing.

Share is of the 2,479 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.

1900s

8
1910s

5
1920s

9
1930s

5
1940s

15
1950s

25
1960s

53
1970s

32
1980s

13
1990s

18
2000s

16
2010s

14
2020s

4

What this shows Construction peaked in the 1960s, when 53 of the county's bridges still in the inventory were built, which is 24.4% of those with a recorded year. That cohort is now 55 to 64 years old in the 2024 inventory. Its average build year is 1969, 10 years older than the Iowa average of 1979.

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

The 5 Iowa counties nearest Harrison County in number of bridges, with their condition splits. Its 18.9% Poor share is the 4th-lowest of these 6. Its average build year of 1969 against a peer-group mean of 1979 is 10 years older.

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

Bridge inventory size and condition shares for Harrison 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
Marion County	217	38.7%	48.8%	12.4%	1984
Ringgold County	217	25.3%	31.3%	43.3%	1971
Harrison County (this page)	217	24.9%	56.2%	18.9%	1969
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 Harrison 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 Harrison 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 (1969 here).

Cook County, IL · avg 1969 · 1,721 bridges
Fresno County, CA · avg 1969 · 916 bridges
Cuyahoga County, OH · avg 1969 · 871 bridges
Ventura County, CA · avg 1969 · 501 bridges

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

All 217 Good 54 Fair 122 Poor 41

Fair-condition bridges (122)

Sort:

Harrison County Bridge Snapshot

Condition distribution

Harrison County's Poor-condition bridges carry 2,479 vehicle crossings a day

60.4% of Harrison County's bridges have passed the 50-year mark

One structure carries 19.7% of the county's Poor-condition bridge traffic

How Harrison 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 (122)

OSAGE TRAIL

MALDEN TRAIL

220TH ST

FM - 335TH ST

FM - 335TH ST

140TH ST

FM & 110TH ST

NORWOOD AVE

YATES AVE

170TH LANE

HILLSIDE AVE

US 30

RUBY TRAIL

IA 127

192 ST

FM NEWARK AVE

US 30

IA 127

FM - 335TH ST

FM & 270TH ST

LOC-SPOKANE AVE

FM & 155TH ST

LOCAL VIENNA AV

US 30

280TH STREET

IA 37

YALE AVE

US 30

NB I-29

SB I-29

FM OVERTON AVE

FM 335TH ST

FM 110 ST

FM - 305TH ST

FM 296TH ST

SEWARD AVE

FM & 194TH ST

305TH ST

SB I-29

NB I-29

SB I-29

FM & 170TH ST

NB I-29

SB I-29

NB I-29

SB I-29

NB I-29

SB I-29

270TH ST

FM & PANORA AVE

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