Total bridges
545
Public highway bridges in Polk County
County profile · official public datasets
Polk County, IA
545 public highway bridges tracked in the FHWA National Bridge Inventory: 57.8% rated Good, 35.8% Fair, 6.4% Poor.
- 545
- Public bridges
- 57.8%
- Good condition
- 6.4%
- Poor condition
The verdict
According to the Federal Highway Administration's 2024 National Bridge Inventory.
Polk County pairs a top-10% lowest Poor-condition share among rated counties in the state with a newer average build year than the state inventory.
- Top 7%
- lowest Poor share in state
- 6.4%
- Poor-condition share
- 545
- public highway bridges
- 1986
- 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.
Polk County Bridge Snapshot
According to the Federal Highway Administration's 2024 National Bridge Inventory, Polk County ranks #7 of 99 Iowa counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 6.4%). Polk County, Iowa contains 545 public highway bridges. Roughly 57.8% are rated “Good,” 35.8% “Fair,” and 6.4% “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
57.8%
315 of 545 rated 7-9
Fair condition
35.8%
195 of 545 rated 5-6
Poor condition
6.4%
35 of 545 rated 4 or below
In-state Poor-share rank
#7 of 99
Among Iowa counties with 5+ bridges, lower share ranks better
Condition distribution
Share of 545 NBI-tracked bridges by lowest applicable component rating.
Good 57.8% (315)
Fair 35.8% (195)
Poor 6.4% (35)
Polk County's Poor-condition bridges carry 81,796 vehicle crossings a day
That is 1.2% of the county's reported daily bridge traffic on 6.3% of its bridges: Poor-condition structures carry less traffic than their share of the inventory. Each Poor bridge averages 2,406 crossings a day against 11,988 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 542 of 545 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.
29.9% of Polk County's bridges have passed the 50-year mark
163 of the 545 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 57.8% 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 19.1% of the county's Poor-condition bridge traffic
FLEUR DR over OLD UP RR & SW 22ND, built 1936, carries 15,634 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 81,796 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.
When Polk County's bridges were built
545 bridges with a recorded construction year, grouped by decade
- 1900s 4
1900–1909
4 bridges
- 1910s 8
1910–1919
8 bridges
- 1920s 9
1920–1929
9 bridges
- 1930s 14
1930–1939
14 bridges
- 1940s 5
1940–1949
5 bridges
- 1950s 43
1950–1959
43 bridges
- 1960s
1960–1969
58 bridges
- 1970s 44
1970–1979
44 bridges
- 1980s 39
1980–1989
39 bridges
- 1990s
1990–1999
103 bridges
- 2000s
2000–2009
142 bridges
- 2010s
2010–2019
64 bridges
- 2020s 12
2020–2029
12 bridges
What this shows Construction peaked in the 2000s, when 142 of the county's bridges still in the inventory were built, which is 26.1% of those with a recorded year. That cohort is now 15 to 24 years old in the 2024 inventory. Its average build year is 1986, 7 years newer than the Iowa average of 1979.
How Polk County compares with Iowa's closest counties by inventory size
The 5 Iowa counties nearest Polk County in number of bridges, with their condition splits. Its 6.4% Poor share is the 3rd-lowest of these 6. Its average build year of 1986 against a peer-group mean of 1984 is in line with the group.
Showing the 5 closest of 98 Iowa counties eligible for comparison.
| County | Bridges | Good | Fair | Poor | Avg. built |
|---|---|---|---|---|---|
| Pottawattamie County | 557 | 38.8% | 51.9% | 9.3% | 1981 |
| Polk County (this page) | 545 | 57.8% | 35.8% | 6.4% | 1986 |
| Linn County | 506 | 46.4% | 47.2% | 6.3% | 1987 |
| Black Hawk County | 489 | 52.8% | 40.7% | 6.5% | 1983 |
| Woodbury County | 455 | 39.3% | 39.6% | 21.1% | 1985 |
| Sioux County | 449 | 62.4% | 34.7% | 2.9% | 1982 |
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 Polk 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 Polk County, both outside Iowa so the neighborhoods are not the same-state size table above.
Similar inventory size
Nearest county inventories outside IA (545 bridges here).
- Grafton County, NH · 544 bridges
- Yavapai County, AZ · 543 bridges
- East Baton Rouge County, LA · 548 bridges
- Kanawha County, WV · 554 bridges
Similar average build year
Nearest mean year-built outside IA (1986 here).
- El Paso County, TX · avg 1986 · 783 bridges
- Caddo County, LA · avg 1986 · 682 bridges
- Weld County, CO · avg 1986 · 614 bridges
- Canadian County, OK · avg 1986 · 493 bridges
Source: FHWA National Bridge Inventory, 2024 release. Peers floor at 10 bridges so stub inventories cannot own the match.
Fair-condition bridges (195)
FM
FairOver: FOUR MILE CREEK
081242201, Polk, IA
Built 1965 Load: 13.5 t ADT: 912
LOCAL RD
FairOver: DEER CREEK
080230903, Polk, IA
Built 1976 Load: 13.6 t ADT: 60
LOCAL ROAD
FairOver: BR. WHITE OAK CK
081230901, Polk, IA
Built 1946 Load: 13.6 t ADT: 45
FM
FairOver: BR BIG CREEK
081251402, Polk, IA
Built 1931 Load: 13.6 t ADT: 259
NE 38TH ST
FairOver: I 80
1.6 MILES E OF E JCT I-35, Polk, IA
Built 1959 Load: 14.4 t ADT: 1,654
JESTER PARK
FairOver: PAW CREEK
081253303, Polk, IA
Built 1963 Load: 14.4 t ADT: 29
NE 158TH
FairOver: I-35
1.9 MILES SOUTH OF IA 210, Polk, IA
Built 1964 Load: 14.8 t ADT: 89
US 69
FairOver: FOURMILE CREEK
0.2 MI. S OF SR F22, Polk, IA
Built 1922 Load: 15.2 t ADT: 6,800
FM
FairOver: DRAINAGE DITCH
080220301, Polk, IA
Built 1959 Load: 15.2 t ADT: 45
NW 146 AVE
FairOver: TURKEY CREEK
0.2 MI. E OF OLD IA 415, Polk, IA
Built 1937 Load: 15.3 t ADT: 71
LOCAL ROAD
FairOver: DRAINAGE DITCH
081221905, Polk, IA
Built 1967 Load: 15.6 t ADT: 40
US 69
FairOver: FOURMILE CREEK
1.3 miles N of IA 160, Polk, IA
Built 1949 Load: 16.1 t ADT: 6,800
NE 96TH ST
FairOver: I-80
1.9 MILES WEST OF SR S27, Polk, IA
Built 1959 Load: 16.4 t ADT: 259
86TH ST
FairOver: N WALNUT CREEK
O62400495, Polk, IA
Built 1968 Load: 16.8 t ADT: 19,687
LOCAL ROAD
FairOver: DITCH
081222902, Polk, IA
Built 1969 Load: 18.0 t ADT: 60
US 6
FairOver: DRAINAGE DITCH
0.9 MILE W OF W JCT IA 28, Polk, IA
Built 1937 Load: 18.1 t ADT: 20,100
I-35 & I-80
FairOver: N WALNUT CREEK
1.1 MILES E OF JCT IA 141, Polk, IA
Built 1958 Load: 18.1 t ADT: 79,500
FM S.E.124TH
FairOver: CAMP CREEK
078222404, Polk, IA
Built 1954 Load: 18.1 t ADT: 71
LOCAL ROAD
FairOver: CAMP CREEK
079222305, Polk, IA
Built 1958 Load: 18.2 t ADT: 34
FM
FairOver: DRAINAGE
081220702, Polk, IA
Built 1967 Load: 18.2 t ADT: 439
FM
FairOver: BRANCH FOUR MILE CREEK
081241001, Polk, IA
Built 1975 Load: 18.7 t ADT: 259
LOCAL RD
FairOver: BRANCH FOUR MILE CREEK
081243504, Polk, IA
Built 1975 Load: 19.1 t ADT: 15
FM NE 80TH ST
FairOver: I-80
2.8 MILES E OF JCT. US 65, Polk, IA
Built 1959 Load: 19.2 t ADT: 638
LOCAL ROAD
FairOver: OLD CHANNEL
081223201, Polk, IA
Built 1969 Load: 19.5 t ADT: 60
WESTERN HILLS D
FairOver: WESTERN HILLS CREEK
000000000, Polk, IA
Built 1994 Load: 20.1 t ADT: 716
LOCAL ROAD
FairOver: FOUR MILE CREEK
081241601, Polk, IA
Built 1926 Load: 20.5 t ADT: 26
NE 142ND
FairOver: I-35
4.0 MILES S OF JCT IA 210, Polk, IA
Built 1964 Load: 21.2 t ADT: 240
NW MADRID DR.
FairOver: BIG CREEK DIV.CHL
081253504, Polk, IA
Built 1970 Load: 21.4 t ADT: 1,314
LOCAL RD
FairOver: BRANCH OF BIG CREEK
081250302, Polk, IA
Built 1975 Load: 21.9 t ADT: 71
AURORA AVE
FairOver: N WALNUT CREEK
O38090555, Polk, IA
Built 1991 Load: 21.9 t ADT: 1,821
LOCAL ROAD
FairOver: MUD CREEK
079221703, Polk, IA
Built 1900 Load: 22.2 t ADT: 210
SB US 65
FairOver: SE 64TH AVE
1.0 MI. N OF JCT. IA 5, Polk, IA
Built 1997 Load: 22.4 t ADT: 10,550
US 65
FairOver: DRAINAGE DITCH
4.5 MILES N OF JCT SR S14, Polk, IA
Built 1978 Load: 22.9 t ADT: 9,600
FM
FairOver: MUCHIKINOCK CREEK
079230901, Polk, IA
Built 1969 Load: 23.0 t ADT: 2,998
NB I-35 EB I-80
FairOver: SAYLOR CREEK
0.5 MI. W OF JCT. 415, Polk, IA
Built 1958 Load: 23.4 t ADT: 43,750
FM
FairOver: FOUR MILE CREEK
080233205, Polk, IA
Built 1966 Load: 23.5 t ADT: 5,776
S 35TH ST
FairOver: STREAM
000000000, Polk, IA
Built 1991 Load: 24.0 t ADT: 1,252
DOUGLAS AVE
FairOver: N WALNUT CREEK
O37600434, Polk, IA
Built 1960 Load: 24.3 t ADT: 10,078
SE 30TH ST
FairOver: UP RR
078230602, Polk, IA
Built 1958 Load: 24.3 t ADT: 9,799
GRAND AVE
FairOver: JORDAN CREEK
000000000, Polk, IA
Built 1996 Load: 24.5 t ADT: 10,266
FM S-27
FairOver: I-80
At Jct. Polk Co. S27, Polk, IA
Built 1959 Load: 24.5 t ADT: 2,978
VALLEY WEST DRIVE
FairOver: JORDAN CREEK
000000000, Polk, IA
Built 1984 Load: 24.6 t ADT: 11,678
US 69
FairOver: RR SCOTT AVE & MLK PKWY
0.7 MILE S OF JCT I-235, Polk, IA
Built 1937 Load: 24.7 t ADT: 33,600
IA 163 EB
FairOver: E 4 MILE CREEK & IAI RR
1.2 MILES W OF JCT US 65, Polk, IA
Built 1965 Load: 24.7 t ADT: 10,750
NE 46TH AVE
FairOver: MUD CREEK
079222001, Polk, IA
Built 1972 Load: 24.9 t ADT: 3,755
FM
FairOver: OLD SKUNK RIV CHANNEL
081223006, Polk, IA
Built 1990 Load: 25.2 t ADT: 967
US 69
FairOver: FOURMILE CREEK
0.3 mi. N of Jct. SR F22, Polk, IA
Built 1949 Load: 25.5 t ADT: 5,200
IA 163 WB
FairOver: E 4 MI IAI RR & N PL HL
1.2 MILES W OF JCT US 65, Polk, IA
Built 1965 Load: 25.5 t ADT: 10,750
SB US 65
FairOver: US 6
1.0 MILE S OF JCT. I-80, Polk, IA
Built 1993 Load: 25.5 t ADT: 10,450
FM
FairOver: SPRING CREEK
078223003, Polk, IA
Built 1968 Load: 25.6 t ADT: 1,215
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.