Total bridges
162
Public highway bridges in Monona County
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.
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.
When Monona County's bridges were built
162 bridges with a recorded construction year, grouped by decade
- 1900s 8
1900–1909
8 bridges
- 1910s 3
1910–1919
3 bridges
- 1920s 1
1920–1929
1 bridges
- 1940s 5
1940–1949
5 bridges
- 1950s
1950–1959
39 bridges
- 1960s
1960–1969
27 bridges
- 1970s
1970–1979
25 bridges
- 1980s 5
1980–1989
5 bridges
- 1990s 10
1990–1999
10 bridges
- 2000s 12
2000–2009
12 bridges
- 2010s
2010–2019
17 bridges
- 2020s 10
2020–2029
10 bridges
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.
| 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
Source: FHWA National Bridge Inventory, 2024 release. Peers floor at 10 bridges so stub inventories cannot own the match.
All bridges (162)
FM
PoorOver: SOLDIER RIVER
082431501, Monona, IA
Built 1955 Load: 17.6 t ADT: 349
FM
PoorOver: WEST FORK DD
085452701, Monona, IA
Built 1961 Load: 18.1 t ADT: 229
FM
PoorOver: LITTLE SIOUX RIVER
085440205, Monona, IA
Built 1925 Load: 18.8 t ADT: 159
FM
PoorOver: MAPLE RIVER
083441504, Monona, IA
Built 1960 Load: 19.8 t ADT: 150
LOCAL
PoorOver: WILLOW CREEK
082420103, Monona, IA
Built 1978 Load: 22.1 t ADT: 11
LOCAL
PoorOver: STREAM
085432701, Monona, IA
Built 1900 Load: 22.1 t ADT: 60
FM
PoorOver: WILLOW CREEK
082422203, Monona, IA
Built 1979 Load: 23.3 t ADT: 199
LOCAL
PoorOver: MCCANDLESS CLEGHORN
084461401, Monona, IA
Built 1976 Load: 24.5 t ADT: 26
LOCAL
PoorOver: STREAM
085420404, Monona, IA
Built 1973 Load: 24.5 t ADT: 80
LOCAL
PoorOver: TRIB TO SOLDIER RIVER
084421103, Monona, IA
Built 1990 Load: 26.8 t ADT: 20
IA 141 & 175
PoorOver: MAPLE RIVER
0.1 mi. E of W jct IA 175, Monona, IA
Built 1967 Load: 29.7 t ADT: 3,640
K53 DOGWOOD AVE
PoorOver: MCCANDLESS CLEGHORN
085462402, Monona, IA
Built 1970 Load: 33.5 t ADT: 20
Read our methodology - how this data is sourced, computed, and verified.
Related
Data sourced from official public datasets. See our methodology for details. Retrieved and formatted by PlainBridges
Every figure on PlainBridges is rendered directly from federal source data, no number is typed in by an editor. This page draws directly on federal source data, no figure is typed in by an editor. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error. NBI condition categories reflect the latest reported inventory record, not a live safety, closure, or travel decision.