County profile · official public datasets

Delaware County, IA

293 public highway bridges tracked in the FHWA National Bridge Inventory: 39.2% rated Good, 53.9% Fair, 6.8% Poor.

293
Public bridges: 39.2%
Good condition: 6.8%
Poor condition

The verdict

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

Delaware County posts a top-10% lowest Poor-condition share among rated counties in the state across mid-size county bridge inventory.

Top 10%
lowest Poor share in state: 6.8%
Poor-condition share: 293
public highway bridges: 1981
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.

Delaware County Bridge Snapshot

According to the Federal Highway Administration's 2024 National Bridge Inventory, Delaware County ranks #10 of 99 Iowa counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 6.8%). Delaware County, Iowa contains 293 public highway bridges. Roughly 39.2% are rated “Good,” 53.9% “Fair,” and 6.8% “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

293

Public highway bridges in Delaware County

Good condition

39.2%

115 of 293 rated 7-9

Fair condition

53.9%

158 of 293 rated 5-6

Poor condition

6.8%

20 of 293 rated 4 or below

In-state Poor-share rank

#10 of 99

Among Iowa counties with 5+ bridges, lower share ranks better

Condition distribution

Share of 293 NBI-tracked bridges by lowest applicable component rating.

Good

39.2% (115)

Fair

53.9% (158)

Poor

6.8% (20)

Delaware County's Poor-condition bridges carry 12,593 vehicle crossings a day

That is 6% of the county's reported daily bridge traffic on 7% of its bridges: Poor-condition structures carry less traffic than their share of the inventory. Each Poor bridge averages 630 crossings a day against 743 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 286 of 293 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.

36.5% of Delaware County's bridges have passed the 50-year mark

107 of the 293 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 39.2% 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 50% of the county's Poor-condition bridge traffic

W MARION ST over MAQUOKETA RIVER, built 1980, carries 6,294 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 20-bridge count understates how much of the daily burden sits on a single crossing.

Share is of the 12,593 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.

1900s

1
1920s

5
1930s

11
1940s

6
1950s

11
1960s

38
1970s

69
1980s

53
1990s

36
2000s

34
2010s

24
2020s

5

What this shows Construction peaked in the 1970s, when 69 of the county's bridges still in the inventory were built, which is 23.5% of those with a recorded year. That cohort is now 45 to 54 years old in the 2024 inventory. Its average build year (1981) matches the Iowa average (1979).

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

The 5 Iowa counties nearest Delaware County in number of bridges, with their condition splits. Its 6.8% Poor share is the 1st-lowest of these 6. Its average build year of 1981 against a peer-group mean of 1978 is in line with the group.

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

Bridge inventory size and condition shares for Delaware County and the 5 Iowa counties closest to it in inventory size
County	Bridges	Good	Fair	Poor	Avg. built
Story County	296	33.1%	53%	13.9%	1968
Cass County	295	25.4%	41%	33.6%	1976
Delaware County (this page)	293	39.2%	53.9%	6.8%	1981
Scott County	291	34.7%	55%	10.3%	1980
Butler County	289	58.1%	26.6%	15.2%	1985
Grundy County	289	42.6%	32.9%	24.6%	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 Delaware 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 Delaware County, both outside Iowa so the neighborhoods are not the same-state size table above.

Similar inventory size

Nearest county inventories outside IA (293 bridges here).

Boone County, IN · 293 bridges
Hocking County, OH · 293 bridges
Franklin County, PA · 294 bridges
Bedford County, TN · 294 bridges

Similar average build year

Nearest mean year-built outside IA (1981 here).

Franklin County, OH · avg 1981 · 922 bridges
Greenville County, SC · avg 1981 · 635 bridges
Montgomery County, OH · avg 1981 · 632 bridges
McLean County, IL · avg 1981 · 624 bridges

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

All 293 Good 115 Fair 158 Poor 20

All bridges (293)

Sort:

Delaware County Bridge Snapshot

Condition distribution

Delaware County's Poor-condition bridges carry 12,593 vehicle crossings a day

36.5% of Delaware County's bridges have passed the 50-year mark

One structure carries 50% of the county's Poor-condition bridge traffic

How Delaware 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 (293)

FM 230TH AVE

LOC FIREFLY RD

FM 140TH AVE

FM 230TH AVE

LOCAL OAK RD

FM 110TH AVE

JOHN ST

LOC 270 AVE

140TH ST

LOCAL 120 AVE

LOCAL 325 ST

LOCAL 330 ST

FM ROCKVILLE RD

LOCAL 180TH AVE

FM 110TH AVE

FM 280 AVE

FM 300 AVE

BACKBONE ST PK

NATURE RD

LOC 122 ST

FM 300TH ST

FM SHERWOOD RD

BACKBONE ST PK

LOCAL 330 ST

300TH AVE

OAK RD

265TH ST

137TH ST

LOC 285 ST

LOCAL 210 AVE

FM 182ND ST

LOCAL 120 ST

FM 332 AVE

LOCAL 320 ST

LOCAL 218 ST

250TH ST

FM 240 ST

FM 240 ST

LOCAL 255 ST

LOCAL 190 ST

LOCAL 280 AVE

FM - 180TH ST

LOC 160 ST

210TH AVE

170TH AVE

LOC 230TH ST

LOCAL 290 AVE

140TH ST

BACKBONE ST PK

IA 3

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