County profile · official public datasets

Mills County, IA

184 public highway bridges tracked in the FHWA National Bridge Inventory: 29.3% rated Good, 51.6% Fair, 19% Poor.

184
Public bridges: 29.3%
Good condition: 19%
Poor condition

The verdict

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

Mills County posts a higher-than-median Poor-condition share among rated counties in the state across mid-size county bridge inventory.

50th
of 99 on Poor share: 19%
Poor-condition share: 184
public highway bridges: 1976
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.

Mills County Bridge Snapshot

According to the Federal Highway Administration's 2024 National Bridge Inventory, Mills County ranks #50 of 99 Iowa counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 19%). Mills County, Iowa contains 184 public highway bridges. Roughly 29.3% are rated “Good,” 51.6% “Fair,” and 19% “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

184

Public highway bridges in Mills County

Good condition

29.3%

54 of 184 rated 7-9

Fair condition

51.6%

95 of 184 rated 5-6

Poor condition

19%

35 of 184 rated 4 or below

In-state Poor-share rank

#50 of 99

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

Condition distribution

Share of 184 NBI-tracked bridges by lowest applicable component rating.

Good

29.3% (54)

Fair

51.6% (95)

Poor

19% (35)

Mills County's Poor-condition bridges carry 4,868 vehicle crossings a day

That is 1.7% of the county's reported daily bridge traffic on 19% of its bridges: Poor-condition structures carry less traffic than their share of the inventory. Each Poor bridge averages 139 crossings a day against 2,557 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 184 of 184 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.

56% of Mills County's bridges have passed the 50-year mark

103 of the 184 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 29.3% 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 31.3% of the county's Poor-condition bridge traffic

FA-BARRUS RD over PONY CREEK, built 1969, carries 1,524 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 35-bridge count understates how much of the daily burden sits on a single crossing.

Share is of the 4,868 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.

1910s

1
1920s

1
1930s

6
1940s

10
1950s

16
1960s

42
1970s

40
1980s

12
1990s

21
2000s

15
2010s

20

What this shows Construction peaked in the 1960s, when 42 of the county's bridges still in the inventory were built, which is 22.8% of those with a recorded year. That cohort is now 55 to 64 years old in the 2024 inventory. Its average build year (1976) matches the Iowa average (1979).

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

The 5 Iowa counties nearest Mills County in number of bridges, with their condition splits. Its 19% Poor share is the 3rd-lowest of these 6. Its average build year of 1976 against a peer-group mean of 1975 is in line with the group.

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

Bridge inventory size and condition shares for Mills County and the 5 Iowa counties closest to it in inventory size
County	Bridges	Good	Fair	Poor	Avg. built
Adams County	186	10.2%	45.2%	44.6%	1967
Osceola County	185	38.4%	53%	8.6%	1965
Mills County (this page)	184	29.3%	51.6%	19%	1976
Appanoose County	183	41%	27.9%	31.1%	1981
Keokuk County	183	34.4%	45.9%	19.7%	1980
Ida County	182	42.9%	40.7%	16.5%	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 Mills 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 Mills County, both outside Iowa so the neighborhoods are not the same-state size table above.

Similar inventory size

Nearest county inventories outside IA (184 bridges here).

Independence County, AR · 184 bridges
Henderson County, KY · 184 bridges
Adams County, OH · 184 bridges
Box Elder County, UT · 184 bridges

Similar average build year

Nearest mean year-built outside IA (1976 here).

Marion County, IN · avg 1976 · 958 bridges
Mohave County, AZ · avg 1976 · 641 bridges
Comanche County, OK · avg 1976 · 593 bridges
Prince George's County, MD · avg 1976 · 576 bridges

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

All 184 Good 54 Fair 95 Poor 35

All bridges (184)

Sort:

Mills County Bridge Snapshot

Condition distribution

Mills County's Poor-condition bridges carry 4,868 vehicle crossings a day

56% of Mills County's bridges have passed the 50-year mark

One structure carries 31.3% of the county's Poor-condition bridge traffic

How Mills 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 (184)

FM-KEYS AVE

MARION AVE

NB I-29

SB I-29

NB I-29

SB I-29

US 34 WB

330TH ST

190TH ST

US 34

US 34 EB

US 34

MAIN ST CO.L-55

221ST STREET

LCL-QUEEN AVE

300TH ST

FM-195TH ST

MASTERS RD

MONTAGUE RD

FA-370TH ST

FM-195TH ST

I-29

M16 370TH ST

221ST STREET

190TH ST

FA-360TH ST

HAZEL ST

NB I-29

SB I-29

FA-245TH ST

FM-APPLEWOOD

FA-JAMISON ROAD

LCL-CARY AVE

FA-GASTON AVE

LCL-BROTHERS AV

US 59

LCL-APPLEWOOD

LAMBERT AVE

NB I-29

SB I-29

NB I-29

SB I-29

QUANDT RD

US 34

LCL-DEACON RD

H38 LAMBERT AVE

LCL-370TH ST

LCL-370TH ST

LCL-COMPASS AVE

LCL-JAHNKE AVE

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