Total bridges
199
Public highway bridges in Dallas County
County profile · official public datasets
Dallas County, IA
199 public highway bridges tracked in the FHWA National Bridge Inventory: 44.7% rated Good, 46.2% Fair, 9% Poor.
- 199
- Public bridges
- 44.7%
- Good condition
- 9%
- Poor condition
The verdict
According to the Federal Highway Administration's 2024 National Bridge Inventory.
Dallas County posts a top-quartile lowest Poor-condition share among rated counties in the state across mid-size county bridge inventory.
- Top 15%
- lowest Poor share in state
- 9%
- Poor-condition share
- 199
- 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.
Dallas County Bridge Snapshot
According to the Federal Highway Administration's 2024 National Bridge Inventory, Dallas County ranks #15 of 99 Iowa counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 9%). Dallas County, Iowa contains 199 public highway bridges. Roughly 44.7% are rated “Good,” 46.2% “Fair,” and 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
44.7%
89 of 199 rated 7-9
Fair condition
46.2%
92 of 199 rated 5-6
Poor condition
9%
18 of 199 rated 4 or below
In-state Poor-share rank
#15 of 99
Among Iowa counties with 5+ bridges, lower share ranks better
Condition distribution
Share of 199 NBI-tracked bridges by lowest applicable component rating.
Good 44.7% (89)
Fair 46.2% (92)
Poor 9% (18)
Dallas County's Poor-condition bridges carry 11,710 vehicle crossings a day
That is 2.1% of the county's reported daily bridge traffic on 9.1% of its bridges: Poor-condition structures carry less traffic than their share of the inventory. Each Poor bridge averages 651 crossings a day against 1,779 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 198 of 199 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.
42.2% of Dallas County's bridges have passed the 50-year mark
84 of the 199 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 44.7% 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 22.4% of the county's Poor-condition bridge traffic
FM over JOHNSON CREEK, built 1933, carries 2,628 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 18-bridge count understates how much of the daily burden sits on a single crossing.
Share is of the 11,710 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.
When Dallas County's bridges were built
199 bridges with a recorded construction year, grouped by decade
- pre-1900 2
Built before 1900
2 bridges
- 1900s 3
1900–1909
3 bridges
- 1910s 5
1910–1919
5 bridges
- 1920s 9
1920–1929
9 bridges
- 1930s 9
1930–1939
9 bridges
- 1940s 5
1940–1949
5 bridges
- 1950s 10
1950–1959
10 bridges
- 1960s
1960–1969
31 bridges
- 1970s
1970–1979
29 bridges
- 1980s
1980–1989
22 bridges
- 1990s
1990–1999
13 bridges
- 2000s
2000–2009
28 bridges
- 2010s
2010–2019
26 bridges
- 2020s 7
2020–2029
7 bridges
What this shows Construction peaked in the 1960s, when 31 of the county's bridges still in the inventory were built, which is 15.6% of those with a recorded year. That cohort is now 55 to 64 years old in the 2024 inventory. Its average build year (1978) matches the Iowa average (1979).
How Dallas County compares with Iowa's closest counties by inventory size
The 5 Iowa counties nearest Dallas County in number of bridges, with their condition splits. Its 9% Poor share is the 1st-lowest of these 6. Its average build year of 1978 against a peer-group mean of 1973 is 5 years newer.
Showing the 5 closest of 98 Iowa counties eligible for comparison.
| County | Bridges | Good | Fair | Poor | Avg. built |
|---|---|---|---|---|---|
| Pocahontas County | 201 | 19.4% | 55.2% | 25.4% | 1974 |
| Dallas County (this page) | 199 | 44.7% | 46.2% | 9% | 1978 |
| Allamakee County | 197 | 31.5% | 59.4% | 9.1% | 1975 |
| Calhoun County | 197 | 24.4% | 50.3% | 25.4% | 1971 |
| Decatur County | 197 | 18.3% | 41.1% | 40.6% | 1972 |
| Page County | 196 | 24% | 43.9% | 32.1% | 1975 |
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 Dallas 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 Dallas County, both outside Iowa so the neighborhoods are not the same-state size table above.
Similar inventory size
Nearest county inventories outside IA (199 bridges here).
- Montgomery County, AR · 199 bridges
- Warren County, IL · 199 bridges
- Leake County, MS · 199 bridges
- Neshoba County, MS · 199 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.
Poor-condition bridges (18)
LOCAL
PoorOver: NORTH RACCOON RIVER
A21600635, Dallas, IA
Built 1882 Load: 0.0 t ADT: 153
COUNTY ROAD
PoorOver: MOSQUITO CREEK
079290805, Dallas, IA
Built 1900 Load: 0.0 t ADT: 21
LOCAL
PoorOver: BEAVER CREEK
081263404, Dallas, IA
Built 1890 Load: 0.0 t ADT: 21
COUNTY ROAD
PoorOver: FROG CREEK
081281608, Dallas, IA
Built 1937 Load: 0.0 t ADT: 35
WARFORD ST
PoorOver: FROG CREEK
081260900, Dallas, IA
Built 1915 Load: 4.4 t ADT: 536
COUNTY ROAD
PoorOver: PANTHER CREEK
079280502, Dallas, IA
Built 1964 Load: 6.9 t ADT: 35
COUNTY ROAD
PoorOver: MOSQUITO CREEK
080290502, Dallas, IA
Built 1942 Load: 7.9 t ADT: 72
LOCAL
PoorOver: PANTHER CREEK
079282201, Dallas, IA
Built 1930 Load: 12.2 t ADT: 60
15TH ST
PoorOver: BUTLER CREEK
079273000, Dallas, IA
Built 1907 Load: 16.1 t ADT: 1,027
PARK RD(SW)
PoorOver: FROG CREEK
081260900, Dallas, IA
Built 1930 Load: 20.0 t ADT: 95
FM
PoorOver: STREAM
080261101, Dallas, IA
Built 1970 Load: 22.3 t ADT: 1,544
FM
PoorOver: JOHNSON CREEK
078262803, Dallas, IA
Built 1933 Load: 22.4 t ADT: 2,628
THOMAS ST
PoorOver: MIDDLE RACOON RIVER
078290400, Dallas, IA
Built 1951 Load: 23.3 t ADT: 574
FM
PoorOver: OVER IAIS RR
078272003, Dallas, IA
Built 1940 Load: 23.7 t ADT: 150
COUNTY ROAD
PoorOver: BRANCH MOSQUITO CREEK
079290803, Dallas, IA
Built 1926 Load: 23.7 t ADT: 21
LOCAL
PoorOver: BEAR CREEK
078283205, Dallas, IA
Built 1949 Load: 24.5 t ADT: 180
F-60
PoorOver: PANTHER CREEK
078280509, Dallas, IA
Built 1966 Load: 27.4 t ADT: 1,930
FM
PoorOver: SUGAR CREEK
078262607, Dallas, IA
Built 1933 Load: 33.3 t ADT: 2,628
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.