Total bridges
304
Public highway bridges in Marshall County
County profile · official public datasets
Marshall County, IA
304 public highway bridges tracked in the FHWA National Bridge Inventory: 32.9% rated Good, 23.7% Fair, 43.4% Poor.
- 304
- Public bridges
- 32.9%
- Good condition
- 43.4%
- Poor condition
The verdict
According to the Federal Highway Administration's 2024 National Bridge Inventory.
Marshall 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.
- 98th
- of 99 on Poor share
- 43.4%
- Poor-condition share
- 304
- public highway bridges
- 1970
- 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.
Marshall County Bridge Snapshot
According to the Federal Highway Administration's 2024 National Bridge Inventory, Marshall County ranks #98 of 99 Iowa counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 43.4%). Marshall County, Iowa contains 304 public highway bridges. Roughly 32.9% are rated “Good,” 23.7% “Fair,” and 43.4% “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
32.9%
100 of 304 rated 7-9
Fair condition
23.7%
72 of 304 rated 5-6
Poor condition
43.4%
132 of 304 rated 4 or below
In-state Poor-share rank
#98 of 99
Among Iowa counties with 5+ bridges, lower share ranks better
Condition distribution
Share of 304 NBI-tracked bridges by lowest applicable component rating.
Good 32.9% (100)
Fair 23.7% (72)
Poor 43.4% (132)
Marshall County's Poor-condition bridges carry 47,789 vehicle crossings a day
That is 13.6% of the county's reported daily bridge traffic on 43.6% of its bridges: Poor-condition structures carry less traffic than their share of the inventory. Each Poor bridge averages 362 crossings a day against 1,912 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 303 of 304 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.
48.4% of Marshall County's bridges have passed the 50-year mark
147 of the 304 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 32.9% 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 21.9% of the county's Poor-condition bridge traffic
SO CENTER ST over LINN CREEK, built 1951, carries 10,448 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 132-bridge count understates how much of the daily burden sits on a single crossing.
Share is of the 47,789 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.
When Marshall County's bridges were built
304 bridges with a recorded construction year, grouped by decade
- 1900s 1
1900–1909
1 bridges
- 1910s
1910–1919
33 bridges
- 1920s 6
1920–1929
6 bridges
- 1930s 15
1930–1939
15 bridges
- 1940s
1940–1949
30 bridges
- 1950s
1950–1959
36 bridges
- 1960s 17
1960–1969
17 bridges
- 1970s
1970–1979
27 bridges
- 1980s
1980–1989
46 bridges
- 1990s
1990–1999
28 bridges
- 2000s
2000–2009
42 bridges
- 2010s 15
2010–2019
15 bridges
- 2020s 8
2020–2029
8 bridges
What this shows Construction peaked in the 1980s, when 46 of the county's bridges still in the inventory were built, which is 15.1% of those with a recorded year. That cohort is now 35 to 44 years old in the 2024 inventory. Its average build year is 1970, 9 years older than the Iowa average of 1979.
How Marshall County compares with Iowa's closest counties by inventory size
The 5 Iowa counties nearest Marshall County in number of bridges, with their condition splits. Its 43.4% Poor share is the 6th-lowest of these 6. Its average build year of 1970 against a peer-group mean of 1980 is 10 years older.
Showing the 5 closest of 98 Iowa counties eligible for comparison.
| County | Bridges | Good | Fair | Poor | Avg. built |
|---|---|---|---|---|---|
| Adair County | 306 | 46.7% | 39.9% | 13.4% | 1983 |
| Marshall County (this page) | 304 | 32.9% | 23.7% | 43.4% | 1970 |
| Chickasaw County | 302 | 42.1% | 30.1% | 27.8% | 1986 |
| Cedar County | 301 | 42.9% | 37.5% | 19.6% | 1983 |
| Crawford County | 301 | 42.5% | 48.5% | 9% | 1982 |
| Story County | 296 | 33.1% | 53% | 13.9% | 1968 |
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 Marshall 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 Marshall County, both outside Iowa so the neighborhoods are not the same-state size table above.
Similar inventory size
Nearest county inventories outside IA (304 bridges here).
- Coles County, IL · 304 bridges
- Knox County, IL · 304 bridges
- Osage County, KS · 304 bridges
- Nobles County, MN · 304 bridges
Similar average build year
Nearest mean year-built outside IA (1970 here).
- Hamilton County, OH · avg 1970 · 783 bridges
- Yavapai County, AZ · avg 1970 · 543 bridges
- Garfield County, OK · avg 1970 · 504 bridges
- San Luis Obispo County, CA · avg 1970 · 401 bridges
Source: FHWA National Bridge Inventory, 2024 release. Peers floor at 10 bridges so stub inventories cannot own the match.
Fair-condition bridges (72)
S 3RD ST
FairOver: UP RR & ST
084183500, Marshall, IA
Built 1984 Load: 36.4 t ADT: 9,000
E MAIN ST
FairOver: LINN CREEK
084182501, Marshall, IA
Built 1972 Load: 36.6 t ADT: 3,399
FM
FairOver: SNIPE CREEK
082193301, Marshall, IA
Built 1980 Load: 37.4 t ADT: 39
SO. 6TH ST.
FairOver: LINN CREEK
083183400, Marshall, IA
Built 1984 Load: 38.1 t ADT: 11,300
DURHAM AVE
FairOver: NORTH SKUNK RIVER
082201006, Marshall, IA
Built 1973 Load: 39.5 t ADT: 113
E SOUTH ST
FairOver: ANSON CREEK
084183501, Marshall, IA
Built 1973 Load: 40.7 t ADT: 1,453
NB IA 14
FairOver: IOWA RIVER
0.8 MILE S OF JCT SR E27, Marshall, IA
Built 1968 Load: 41.0 t ADT: 2,950
IA 330
FairOver: CLEAR CREEK
1.8 MI. S OF S JCT SR S52, Marshall, IA
Built 1979 Load: 41.5 t ADT: 4,150
FM
FairOver: MINERVA CREEK
084200202, Marshall, IA
Built 1995 Load: 42.3 t ADT: 363
FM
FairOver: MIDDLE MINERVA CREEK
084200403, Marshall, IA
Built 2005 Load: 42.3 t ADT: 147
FM
FairOver: BIG MINERVA CREEK
085202606, Marshall, IA
Built 1999 Load: 42.3 t ADT: 187
FM
FairOver: N TIMBER CR
083170808, Marshall, IA
Built 1989 Load: 42.9 t ADT: 157
FM
FairOver: MUD CREEK
085191903, Marshall, IA
Built 1967 Load: 44.0 t ADT: 265
LOCAL
FairOver: BR MINERVA CREEK
084190601, Marshall, IA
Built 1988 Load: 45.4 t ADT: 20
LOCAL
FairOver: LINN CR
084193101, Marshall, IA
Built 1989 Load: 47.7 t ADT: 41
FM
FairOver: TIMBER CREEK
083171704, Marshall, IA
Built 1991 Load: 48.1 t ADT: 187
E NEVADA ST
FairOver: LINN CREEK
084183600, Marshall, IA
Built 1987 Load: 49.1 t ADT: 5,041
IA 14
FairOver: UP RR MADISON&MARKET ST
IN MARSHALLTOWN, Marshall, IA
Built 1985 Load: 50.2 t ADT: 13,300
SB IA 14
FairOver: IOWA RIVER
0.8 MILE SOUTH OF SR E27, Marshall, IA
Built 1987 Load: 50.6 t ADT: 2,950
LOCAL
FairOver: SOUTH TIMBER CREEK
082181702, Marshall, IA
Built 1971 Load: 69.3 t ADT: 30
FM
FairOver: NORTH SKUNK RIVER
083202106, Marshall, IA
Built 1965 Load: 99.9 t ADT: 628
FM
FairOver: CREEK
085173402, Marshall, IA
Built 1963 Load: 99.9 t ADT: 1,483
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.