County profile · official public datasets

Black Hawk County, IA

489 public highway bridges tracked in the FHWA National Bridge Inventory: 52.8% rated Good, 40.7% Fair, 6.5% Poor.

489
Public bridges: 52.8%
Good condition: 6.5%
Poor condition

The verdict

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

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

Top 8%
lowest Poor share in state: 6.5%
Poor-condition share: 489
public highway bridges: 1983
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.

Black Hawk County Bridge Snapshot

According to the Federal Highway Administration's 2024 National Bridge Inventory, Black Hawk County ranks #8 of 99 Iowa counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 6.5%). Black Hawk County, Iowa contains 489 public highway bridges. Roughly 52.8% are rated “Good,” 40.7% “Fair,” and 6.5% “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

489

Public highway bridges in Black Hawk County

Good condition

52.8%

258 of 489 rated 7-9

Fair condition

40.7%

199 of 489 rated 5-6

Poor condition

6.5%

32 of 489 rated 4 or below

In-state Poor-share rank

#8 of 99

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

Condition distribution

Share of 489 NBI-tracked bridges by lowest applicable component rating.

Good

52.8% (258)

Fair

40.7% (199)

Poor

6.5% (32)

Black Hawk County's Poor-condition bridges carry 34,702 vehicle crossings a day

That is 2.2% of the county's reported daily bridge traffic on 6.6% of its bridges: Poor-condition structures carry less traffic than their share of the inventory. Each Poor bridge averages 1,084 crossings a day against 3,129 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 488 of 489 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.

29% of Black Hawk County's bridges have passed the 50-year mark

142 of the 489 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 52.8% 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 24.2% of the county's Poor-condition bridge traffic

E RIDGEWAY AVE over DRY RUN CREEK, built 1950, carries 8,392 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 32-bridge count understates how much of the daily burden sits on a single crossing.

Share is of the 34,702 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.

1900s

8
1920s

4
1930s

5
1940s

20
1950s

38
1960s

39
1970s

45
1980s

122
1990s

92
2000s

67
2010s

37
2020s

12

What this shows Construction peaked in the 1980s, when 122 of the county's bridges still in the inventory were built, which is 24.9% of those with a recorded year. That cohort is now 35 to 44 years old in the 2024 inventory. Its average build year (1983) matches the Iowa average (1979).

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

The 5 Iowa counties nearest Black Hawk County in number of bridges, with their condition splits. Its 6.5% Poor share is the 4th-lowest of these 6. Its average build year of 1983 against a peer-group mean of 1983 is in line with the group.

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

Bridge inventory size and condition shares for Black Hawk County and the 5 Iowa counties closest to it in inventory size
County	Bridges	Good	Fair	Poor	Avg. built
Polk County	545	57.8%	35.8%	6.4%	1986
Linn County	506	46.4%	47.2%	6.3%	1987
Black Hawk County (this page)	489	52.8%	40.7%	6.5%	1983
Woodbury County	455	39.3%	39.6%	21.1%	1985
Sioux County	449	62.4%	34.7%	2.9%	1982
Plymouth County	432	52.1%	26.4%	21.5%	1974

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

Similar inventory size

Nearest county inventories outside IA (489 bridges here).

Suffolk County, MA · 489 bridges
Shasta County, CA · 492 bridges
Lyon County, KS · 492 bridges
St. Clair County, IL · 486 bridges

Similar average build year

Nearest mean year-built outside IA (1983 here).

Dallas County, TX · avg 1983 · 3,230 bridges
Bexar County, TX · avg 1983 · 2,342 bridges
Sedgwick County, KS · avg 1983 · 1,333 bridges
Will County, IL · avg 1983 · 649 bridges

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

All 489 Good 258 Fair 199 Poor 32

Good-condition bridges (258)

Sort:

Black Hawk County Bridge Snapshot

Condition distribution

Black Hawk County's Poor-condition bridges carry 34,702 vehicle crossings a day

29% of Black Hawk County's bridges have passed the 50-year mark

One structure carries 24.2% of the county's Poor-condition bridge traffic

How Black Hawk 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 (258)

IA 281

I 380 SB

NB I-380

NB IA 27

FM V-51

SB IA 58

SPRING CREEK RD

20TH ST

ELDORA RD.NE

NW RAMP

YOUNG RD

W MT VERNON RD

UNIVERSITY AVE

S TO W RAMP

GREENHILL RD

US 63

NB US 218

WAGNER RD

WB US 20

US 218

MAIN ST

IA 281

W CEDAR-WAPSI RD

GREENHILL RD

WATERBURY DR

TECHNOLOGY PKWY

WYNNEWOOD DR

C 57

US 63

VIKING ROAD

ELDORA RD.SW

MAIN ST

IA 57

BRANDON RD

HOLMES RD

GILBERTVILLE RD

ZANETA RD

HESS RD

BURTON AVE

ALEXANDRA DRIVE

IA 27 & RAMPS

IA 27/58

SB IA 27

RAMP A (SB)

WEIDEN RD

WB US 20

I 380 NB

KLINE RD

W QUARRY RD

W REINBECK RD

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