County profile · official public datasets

Mitchell County, IA

167 public highway bridges tracked in the FHWA National Bridge Inventory: 47.3% rated Good, 42.5% Fair, 10.2% Poor.

167
Public bridges: 47.3%
Good condition: 10.2%
Poor condition

The verdict

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

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

Top 20%
lowest Poor share in state: 10.2%
Poor-condition share: 167
public highway bridges: 1980
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.

Mitchell County Bridge Snapshot

According to the Federal Highway Administration's 2024 National Bridge Inventory, Mitchell County ranks #20 of 99 Iowa counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 10.2%). Mitchell County, Iowa contains 167 public highway bridges. Roughly 47.3% are rated “Good,” 42.5% “Fair,” and 10.2% “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

167

Public highway bridges in Mitchell County

Good condition

47.3%

79 of 167 rated 7-9

Fair condition

42.5%

71 of 167 rated 5-6

Poor condition

10.2%

17 of 167 rated 4 or below

In-state Poor-share rank

#20 of 99

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

Condition distribution

Share of 167 NBI-tracked bridges by lowest applicable component rating.

Good

47.3% (79)

Fair

42.5% (71)

Poor

10.2% (17)

Mitchell County's Poor-condition bridges carry 3,938 vehicle crossings a day

That is 6.6% of the county's reported daily bridge traffic on 10.2% of its bridges: Poor-condition structures carry less traffic than their share of the inventory. Each Poor bridge averages 232 crossings a day against 392 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 167 of 167 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.

37.1% of Mitchell County's bridges have passed the 50-year mark

62 of the 167 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 47.3% 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 25.7% of the county's Poor-condition bridge traffic

LANCER AVE over SMALL NATURAL STREAM, built 1925, carries 1,011 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 17-bridge count understates how much of the daily burden sits on a single crossing.

Share is of the 3,938 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.

1900s

1
1910s

2
1920s

6
1930s

8
1940s

1
1950s

12
1960s

10
1970s

44
1980s

23
1990s

19
2000s

21
2010s

16
2020s

4

What this shows Construction peaked in the 1970s, when 44 of the county's bridges still in the inventory were built, which is 26.3% of those with a recorded year. That cohort is now 45 to 54 years old in the 2024 inventory. Its average build year (1980) matches the Iowa average (1979).

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

The 5 Iowa counties nearest Mitchell County in number of bridges, with their condition splits. Its 10.2% Poor share is the 1st-lowest of these 6. Its average build year of 1980 against a peer-group mean of 1977 is in line with the group.

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

Bridge inventory size and condition shares for Mitchell County and the 5 Iowa counties closest to it in inventory size
County	Bridges	Good	Fair	Poor	Avg. built
Union County	169	30.2%	37.3%	32.5%	1978
Clarke County	168	27.4%	41.1%	31.5%	1977
Greene County	168	35.1%	50%	14.9%	1973
Mitchell County (this page)	167	47.3%	42.5%	10.2%	1980
Davis County	165	44.8%	29.7%	25.5%	1985
Hamilton County	165	39.4%	40%	20.6%	1970

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

Similar inventory size

Nearest county inventories outside IA (167 bridges here).

Cherokee County, AL · 167 bridges
Garfield County, CO · 167 bridges
Ness County, KS · 167 bridges
Gratiot County, MI · 167 bridges

Similar average build year

Nearest mean year-built outside IA (1980 here).

Tulsa County, OK · avg 1980 · 1,135 bridges
Miami-Dade County, FL · avg 1980 · 1,057 bridges
Pulaski County, AR · avg 1980 · 721 bridges
McLennan County, TX · avg 1980 · 714 bridges

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

All 167 Good 79 Fair 71 Poor 17

Good-condition bridges (79)

Sort:

Mitchell County Bridge Snapshot

Condition distribution

Mitchell County's Poor-condition bridges carry 3,938 vehicle crossings a day

37.1% of Mitchell County's bridges have passed the 50-year mark

One structure carries 25.7% of the county's Poor-condition bridge traffic

How Mitchell 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 (79)

US 218

405TH

HICKORY AVE

US 218

330TH

US 218

DANCER AVE

IA 9

430TH

340TH

370TH

FOOTHILL AVE

340TH ST

A43 390TH ST

380TH

370TH

440TH

TIMBER AVE

450TH ST

465TH

WINDFALL AVE

OCEAN AVE

DANCER AVE

MARCH AVE

440TH

380TH

500TH

SHADOW AVE

440TH

IA 9

T34 JERSEY AVE

317TH ST

OLD IA 105

VALLEY AVE

NOBLE AVE

319TH

316TH

340TH

UNDERWOOD AVE

NOBLE AVE

385TH

ECHO AVE

LOCAL

TIMBER AVE

TIMBER AVE

QUAIL AVE

QUAIL AVE

MARCH AVE

T28 HICKORY AVE

ZINNIA AVE

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