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.

Total bridges

199

Public highway bridges in Dallas County

Good condition

44.7%

89 of 199 rated 7-9

Fair condition

46.2%

92 of 199 rated 5-6

Poor condition

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.

pre-1900

2
1900s

3
1910s

5
1920s

9
1930s

9
1940s

5
1950s

10
1960s

31
1970s

29
1980s

22
1990s

13
2000s

28
2010s

26
2020s

7

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.

Bridge inventory size and condition shares for Dallas County and the 5 Iowa counties closest to it in inventory size
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.

All 199 Good 89 Fair 92 Poor 18

All bridges (199)

Sort:

Dallas County Bridge Snapshot

Condition distribution

Dallas County's Poor-condition bridges carry 11,710 vehicle crossings a day

42.2% of Dallas County's bridges have passed the 50-year mark

One structure carries 22.4% of the county's Poor-condition bridge traffic

How Dallas 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

All bridges (199)

STATE ST

S GRAND PRAIRIE

LOCAL

COUNTY ROAD

LOCAL

JORDAN CREEK PKWY

COUNTY ROAD

WILLIS AVE

STAGECOACH DR

GRAND AVE

EB IA 141

220TH ST

JEWEL CIR

FILMORE CT

360TH STREET

D AVE

LOCAL

GRAND PRAIRIE PKWY

BOONEVILLE RD

GRAND AVE

COUNTRY ROAD

LOCAL

LOCAL

COUNTY ROAD

156TH ST

156TH ST

FM

FM

COUNTY ROAD

I-80

I-80

LOCAL

COUNTY ROAD

LOCAL

COUNTY ROAD

WARFORD ST

COUNTY ROAD

COUNTY ROAD

LOCAL

15TH ST

PARK RD(SW)

FM

FM

THOMAS ST

FM

COUNTY ROAD

LOCAL

F-60

FM

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