County profile · official public datasets

Monona County, IA

162 public highway bridges tracked in the FHWA National Bridge Inventory: 36.4% rated Good, 38.3% Fair, 25.3% Poor.

162
Public bridges: 36.4%
Good condition: 25.3%
Poor condition

The verdict

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

Monona County pairs a higher-than-median Poor-condition share among rated counties in the state with an older average build year than the state inventory.

70th
of 99 on Poor share: 25.3%
Poor-condition share: 162
public highway bridges: 1973
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.

Monona County Bridge Snapshot

According to the Federal Highway Administration's 2024 National Bridge Inventory, Monona County ranks #70 of 99 Iowa counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 25.3%). Monona County, Iowa contains 162 public highway bridges. Roughly 36.4% are rated “Good,” 38.3% “Fair,” and 25.3% “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

162

Public highway bridges in Monona County

Good condition

36.4%

59 of 162 rated 7-9

Fair condition

38.3%

62 of 162 rated 5-6

Poor condition

25.3%

41 of 162 rated 4 or below

In-state Poor-share rank

#70 of 99

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

Condition distribution

Share of 162 NBI-tracked bridges by lowest applicable component rating.

Good

36.4% (59)

Fair

38.3% (62)

Poor

25.3% (41)

Monona County's Poor-condition bridges carry 8,234 vehicle crossings a day

That is 8.6% of the county's reported daily bridge traffic on 25.3% of its bridges: Poor-condition structures carry less traffic than their share of the inventory. Each Poor bridge averages 201 crossings a day against 906 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 162 of 162 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.

61.7% of Monona County's bridges have passed the 50-year mark

100 of the 162 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 36.4% 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 44.2% of the county's Poor-condition bridge traffic

IA 141 & 175 over MAPLE RIVER, built 1967, carries 3,640 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 41-bridge count understates how much of the daily burden sits on a single crossing.

Share is of the 8,234 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.

1900s

8
1910s

3
1920s

1
1940s

5
1950s

39
1960s

27
1970s

25
1980s

5
1990s

10
2000s

12
2010s

17
2020s

10

What this shows Construction peaked in the 1950s, when 39 of the county's bridges still in the inventory were built, which is 24.1% of those with a recorded year. That cohort is now 65 to 74 years old in the 2024 inventory. Its average build year is 1973, 6 years older than the Iowa average of 1979.

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

The 5 Iowa counties nearest Monona County in number of bridges, with their condition splits. Its 25.3% Poor share is the 5th-lowest of these 6. Its average build year of 1973 against a peer-group mean of 1981 is 8 years older.

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

Bridge inventory size and condition shares for Monona County and the 5 Iowa counties closest to it in inventory size
County	Bridges	Good	Fair	Poor	Avg. built
Mitchell County	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
Wayne County	163	44.2%	37.4%	18.4%	1989
Monona County (this page)	162	36.4%	38.3%	25.3%	1973
Jefferson County	157	43.9%	37.6%	18.5%	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 Monona 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 Monona County, both outside Iowa so the neighborhoods are not the same-state size table above.

Similar inventory size

Nearest county inventories outside IA (162 bridges here).

Perry County, AL · 162 bridges
Johnson County, AR · 162 bridges
Ouachita County, AR · 162 bridges
Bond County, IL · 162 bridges

Similar average build year

Nearest mean year-built outside IA (1973 here).

Jefferson County, AL · avg 1973 · 1,068 bridges
Erie County, NY · avg 1973 · 906 bridges
Davidson County, TN · avg 1973 · 832 bridges
Lancaster County, PA · avg 1973 · 801 bridges

Fair

Over: SMALL STREAM

085431403, Monona, IA

Monona County Bridge Snapshot

Condition distribution

Monona County's Poor-condition bridges carry 8,234 vehicle crossings a day

61.7% of Monona County's bridges have passed the 50-year mark

One structure carries 44.2% of the county's Poor-condition bridge traffic

How Monona 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 (162)

FM

IA 37

IA 175

IA 183

FM

IA 175

FM

LOCAL

FM

FM

LOCAL

LOCAL RD

FM

FM

IA 175

IA 175

IA 175

FM

FM

IA 175

IA 183

IA 183

IA 175

IA 175

IA 175

IA 183

IA 183

K45

NB I-29

NB I-29

TEAK AVE

E54

E54

TULIP AVE

LOCAL

SUMAC AVE

105TH ST

E 34

FM

LOCAL

170TH ST

E64 REDWOOD AVE

245TH ST

FM

FM

FM

FM

WEST ST

FM

LOCAL ROAD

Related