Total bridges
217
Public highway bridges in Harrison County
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.
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.
When Harrison County's bridges were built
217 bridges with a recorded construction year, grouped by decade
- 1900s 8
1900–1909
8 bridges
- 1910s 5
1910–1919
5 bridges
- 1920s 9
1920–1929
9 bridges
- 1930s 5
1930–1939
5 bridges
- 1940s 15
1940–1949
15 bridges
- 1950s
1950–1959
25 bridges
- 1960s
1960–1969
53 bridges
- 1970s
1970–1979
32 bridges
- 1980s 13
1980–1989
13 bridges
- 1990s 18
1990–1999
18 bridges
- 2000s 16
2000–2009
16 bridges
- 2010s 14
2010–2019
14 bridges
- 2020s 4
2020–2029
4 bridges
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.
| 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.
Good-condition bridges (54)
IA 44
GoodOver: PIGEON CREEK
7.0 mi. E of US 30, Harrison, IA
Built 1978 Load: 55.5 t ADT: 800
315TH ST
GoodOver: KEG CREEK
078412301, Harrison, IA
Built 1999 Load: 58.0 t ADT: 20
SPOKANE AVE
GoodOver: MILL CREEK
081412104, Harrison, IA
Built 2003 Load: 58.0 t ADT: 45
IA 44
GoodOver: BRANCH SIX MILE CREEK
4.3 MI. E OF JCT. US 30, Harrison, IA
Built 1978 Load: 99.9 t ADT: 800
Read our methodology - how this data is sourced, computed, and verified.
Related
Data sourced from official public datasets. See our methodology for details. Retrieved and formatted by PlainBridges
Every figure on PlainBridges is rendered directly from federal source data, no number is typed in by an editor. This page draws directly on federal source data, no figure is typed in by an editor. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error. NBI condition categories reflect the latest reported inventory record, not a live safety, closure, or travel decision.