Total bridges
184
Public highway bridges in Mills County
County profile · official public datasets
Mills County, IA
184 public highway bridges tracked in the FHWA National Bridge Inventory: 29.3% rated Good, 51.6% Fair, 19% Poor.
- 184
- Public bridges
- 29.3%
- Good condition
- 19%
- Poor condition
The verdict
According to the Federal Highway Administration's 2024 National Bridge Inventory.
Mills County posts a higher-than-median Poor-condition share among rated counties in the state across mid-size county bridge inventory.
- 50th
- of 99 on Poor share
- 19%
- Poor-condition share
- 184
- public highway bridges
- 1976
- 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.
Mills County Bridge Snapshot
According to the Federal Highway Administration's 2024 National Bridge Inventory, Mills County ranks #50 of 99 Iowa counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 19%). Mills County, Iowa contains 184 public highway bridges. Roughly 29.3% are rated “Good,” 51.6% “Fair,” and 19% “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
29.3%
54 of 184 rated 7-9
Fair condition
51.6%
95 of 184 rated 5-6
Poor condition
19%
35 of 184 rated 4 or below
In-state Poor-share rank
#50 of 99
Among Iowa counties with 5+ bridges, lower share ranks better
Condition distribution
Share of 184 NBI-tracked bridges by lowest applicable component rating.
Good 29.3% (54)
Fair 51.6% (95)
Poor 19% (35)
Mills County's Poor-condition bridges carry 4,868 vehicle crossings a day
That is 1.7% of the county's reported daily bridge traffic on 19% of its bridges: Poor-condition structures carry less traffic than their share of the inventory. Each Poor bridge averages 139 crossings a day against 2,557 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 184 of 184 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.
56% of Mills County's bridges have passed the 50-year mark
103 of the 184 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 29.3% 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 31.3% of the county's Poor-condition bridge traffic
FA-BARRUS RD over PONY CREEK, built 1969, carries 1,524 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 35-bridge count understates how much of the daily burden sits on a single crossing.
Share is of the 4,868 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.
When Mills County's bridges were built
184 bridges with a recorded construction year, grouped by decade
- 1910s 1
1910–1919
1 bridges
- 1920s 1
1920–1929
1 bridges
- 1930s 6
1930–1939
6 bridges
- 1940s 10
1940–1949
10 bridges
- 1950s 16
1950–1959
16 bridges
- 1960s
1960–1969
42 bridges
- 1970s
1970–1979
40 bridges
- 1980s 12
1980–1989
12 bridges
- 1990s
1990–1999
21 bridges
- 2000s 15
2000–2009
15 bridges
- 2010s
2010–2019
20 bridges
What this shows Construction peaked in the 1960s, when 42 of the county's bridges still in the inventory were built, which is 22.8% of those with a recorded year. That cohort is now 55 to 64 years old in the 2024 inventory. Its average build year (1976) matches the Iowa average (1979).
How Mills County compares with Iowa's closest counties by inventory size
The 5 Iowa counties nearest Mills County in number of bridges, with their condition splits. Its 19% Poor share is the 3rd-lowest of these 6. Its average build year of 1976 against a peer-group mean of 1975 is in line with the group.
Showing the 5 closest of 98 Iowa counties eligible for comparison.
| County | Bridges | Good | Fair | Poor | Avg. built |
|---|---|---|---|---|---|
| Adams County | 186 | 10.2% | 45.2% | 44.6% | 1967 |
| Osceola County | 185 | 38.4% | 53% | 8.6% | 1965 |
| Mills County (this page) | 184 | 29.3% | 51.6% | 19% | 1976 |
| Appanoose County | 183 | 41% | 27.9% | 31.1% | 1981 |
| Keokuk County | 183 | 34.4% | 45.9% | 19.7% | 1980 |
| Ida County | 182 | 42.9% | 40.7% | 16.5% | 1983 |
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 Mills 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 Mills County, both outside Iowa so the neighborhoods are not the same-state size table above.
Similar inventory size
Nearest county inventories outside IA (184 bridges here).
- Independence County, AR · 184 bridges
- Henderson County, KY · 184 bridges
- Adams County, OH · 184 bridges
- Box Elder County, UT · 184 bridges
Similar average build year
Nearest mean year-built outside IA (1976 here).
- Marion County, IN · avg 1976 · 958 bridges
- Mohave County, AZ · avg 1976 · 641 bridges
- Comanche County, OK · avg 1976 · 593 bridges
- Prince George's County, MD · avg 1976 · 576 bridges
Source: FHWA National Bridge Inventory, 2024 release. Peers floor at 10 bridges so stub inventories cannot own the match.
Good-condition bridges (54)
H38 LAMBERT AVE
GoodOver: NISHNABOTNA
072413501, Mills, IA
Built 2012 Load: 53.5 t ADT: 289
LCL-370TH ST
GoodOver: DEER CREEK
071402002, Mills, IA
Built 2005 Load: 54.2 t ADT: 15
LCL-370TH ST
GoodOver: DEER CREEK
071402002, Mills, IA
Built 2005 Load: 56.7 t ADT: 15
LCL-COMPASS AVE
GoodOver: STREAM
073411403, Mills, IA
Built 2000 Load: 82.9 t ADT: 11
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.