County profile · official public datasets

Dubuque County, IA

346 public highway bridges tracked in the FHWA National Bridge Inventory: 50.6% rated Good, 40.8% Fair, 8.7% Poor.

346
Public bridges: 50.6%
Good condition: 8.7%
Poor condition

The verdict

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

Dubuque County pairs a top-quartile lowest Poor-condition share among rated counties in the state with a newer average build year than the state inventory.

Top 13%
lowest Poor share in state: 8.7%
Poor-condition share: 346
public highway bridges: 1989
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.

Dubuque County Bridge Snapshot

According to the Federal Highway Administration's 2024 National Bridge Inventory, Dubuque County ranks #13 of 99 Iowa counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 8.7%). Dubuque County, Iowa contains 346 public highway bridges. Roughly 50.6% are rated “Good,” 40.8% “Fair,” and 8.7% “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

346

Public highway bridges in Dubuque County

Good condition

50.6%

175 of 346 rated 7-9

Fair condition

40.8%

141 of 346 rated 5-6

Poor condition

8.7%

30 of 346 rated 4 or below

In-state Poor-share rank

#13 of 99

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

Condition distribution

Share of 346 NBI-tracked bridges by lowest applicable component rating.

Good

50.6% (175)

Fair

40.8% (141)

Poor

8.7% (30)

Dubuque County's Poor-condition bridges carry 9,093 vehicle crossings a day

That is 1.2% of the county's reported daily bridge traffic on 8.7% of its bridges: Poor-condition structures carry less traffic than their share of the inventory. Each Poor bridge averages 303 crossings a day against 2,143 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 345 of 346 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.

23.1% of Dubuque County's bridges have passed the 50-year mark

80 of the 346 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 50.6% 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 20.6% of the county's Poor-condition bridge traffic

OLD IA 966 over OVER CC RR, built 1936, carries 1,876 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 30-bridge count understates how much of the daily burden sits on a single crossing.

Share is of the 9,093 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.

pre-1900

1
1900s

5
1910s

2
1920s

8
1930s

10
1940s

12
1950s

11
1960s

16
1970s

30
1980s

50
1990s

49
2000s

50
2010s

84
2020s

18

What this shows Construction peaked in the 2010s, when 84 of the county's bridges still in the inventory were built, which is 24.3% of those with a recorded year. That cohort is now 5 to 14 years old in the 2024 inventory. Its average build year is 1989, 10 years newer than the Iowa average of 1979.

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

The 5 Iowa counties nearest Dubuque County in number of bridges, with their condition splits. Its 8.7% Poor share is the 2nd-lowest of these 6. Its average build year of 1989 against a peer-group mean of 1976 is 13 years newer.

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

Bridge inventory size and condition shares for Dubuque County and the 5 Iowa counties closest to it in inventory size
County	Bridges	Good	Fair	Poor	Avg. built
Clinton County	372	66.7%	30.4%	3%	1986
Johnson County	372	39.5%	50.3%	10.2%	1979
Fayette County	362	35.1%	40.3%	24.6%	1974
Dubuque County (this page)	346	50.6%	40.8%	8.7%	1989
Winneshiek County	342	37.1%	45.3%	17.5%	1967
Tama County	337	34.4%	31.2%	34.4%	1976

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 Dubuque 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 Dubuque County, both outside Iowa so the neighborhoods are not the same-state size table above.

Similar inventory size

Nearest county inventories outside IA (346 bridges here).

Macon County, IL · 346 bridges
Whitman County, WA · 347 bridges
Navarro County, TX · 345 bridges
Fillmore County, MN · 348 bridges

Similar average build year

Nearest mean year-built outside IA (1989 here).

Harris County, TX · avg 1989 · 4,029 bridges
Mecklenburg County, NC · avg 1989 · 746 bridges
Buffalo County, NE · avg 1989 · 459 bridges
Brazos County, TX · avg 1989 · 370 bridges

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

All 346 Good 175 Fair 141 Poor 30

Good-condition bridges (175)

Sort:

Dubuque County Bridge Snapshot

Condition distribution

Dubuque County's Poor-condition bridges carry 9,093 vehicle crossings a day

23.1% of Dubuque County's bridges have passed the 50-year mark

One structure carries 20.6% of the county's Poor-condition bridge traffic

How Dubuque 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

Good-condition bridges (175)

IA 946 NB

BOBCAT RD

IA 3

US 20 RAMPS

ARENSDORF RD

OLDE MASSEY RD

BIERMAN RD

Y21 BUDD RD

3RD ST

US 151 (NB/EB)

MAIN ST

PAPE RD

BOY SCOUT RD

MILLVILLE RD

FREMONT AVE

HILL-BRYANT ST

WORTHINGTON RD

US 151 SB

STEGER RD

DURANGO RD

FLANNAGAN RD

RHOMBERG AVE

US 151 SB

US 151 NB

US 151 SB

BUNCOMBE RD

KARPER HARBOR RD

COTTINGHAM RD

CHESTERMAN RD

PILOT GROVE RD

E WORTHINGTON

HALES MILL RD

DERBY GRANGE RD

HICKORY VALLEY RD

PLUM CREEK RD

MINES OF SPAIN

LEUCHS RD

HAMMERAND RD

EAST 22ND ST

WORTHINGTON RD

HANNAH RD

BOCKENSTEDT

FLANNAGAN RD

X71 CLEAR CREEK RD

HOSCH RD

Y17 GUN CLUB RD

CHRISTOPH RD

CLEAR CREEK RD

COTTINGHAM RD

FENGLER ST

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