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.

Total bridges

545

Public highway bridges in Polk County

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

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.

Source FHWA National Bridge Inventory (year built) As of 2024 NBI release

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.

Bridge inventory size and condition shares for Polk County and the 5 Iowa counties closest to it in inventory size
County Bridges Poor
Pottawattamie County 557 9.3%
Polk County (this page) 545 6.4%
Linn County 506 6.3%
Black Hawk County 489 6.5%
Woodbury County 455 21.1%
Sioux County 449 2.9%

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).

Similar average build year

Nearest mean year-built outside IA (1986 here).

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

All 545 Good 315 Fair 195 Poor 35

All bridges (545)

WB I-235

Good

Over: UP RR

0.2 MILE E OF JCT IA 163, Polk, IA

Built 2004 Load: 54.2 t ADT: 35,150

I 35

Good

Over: TRIB TO FOUR MILE CREEK

0.8 MI. N OF E 1ST ST, Polk, IA

Built 2018 Load: 54.4 t ADT: 56,800

EASTON BLVD

Good

Over: FOUR MILE CREEK

0792332, Polk, IA

Built 2011 Load: 55.3 t ADT: 7,802

WB I-235

Good

Over: GUTHRIE AVE

1.2 MILES E OF JCT IA 163, Polk, IA

Built 2006 Load: 57.6 t ADT: 33,900

EB I-235

Good

Over: KEO WAY

3.6 mi. E of Jct. IA 28, Polk, IA

Built 2006 Load: 61.8 t ADT: 42,800

19TH ST RAMP

Good

Over: KEO WAY

3.6 MILES E OF JCT IA 28, Polk, IA

Built 2004 Load: 64.7 t ADT: 12,200

US 6 EB

Good

Over: WALNUT CREEK/BIKE PATH

1.0 MI. W OF JCT. I-35/80, Polk, IA

Built 1998 Load: 67.1 t ADT: 15,350

US 6 WB

Good

Over: WALNUT CREEK/BIKE PATH

1.0 MI W OF JCT I-35/80, Polk, IA

Built 1998 Load: 67.1 t ADT: 15,350

EB I-235

Good

Over: NB US 69/E 15TH ST

AT JUNCTION WITH US 69, Polk, IA

Built 2004 Load: 67.8 t ADT: 38,550

WB I-235

Good

Over: KEO WAY

3.6 MILES E OF JCT. IA 28, Polk, IA

Built 2005 Load: 70.9 t ADT: 36,850

FM SW MCKINLEY

Poor

Over: FRINK CREEK

078252500, Polk, IA

Built 1937 Load: 0.0 t ADT: 245

LOCAL ROAD

Poor

Over: FOUR MILE CREEK

080233005, Polk, IA

Built 1941 Load: 0.0 t ADT: 89

FM

Poor

Over: BRANCH SKUNK RIVER

081231301, Polk, IA

Built 1968 Load: 8.1 t ADT: 139

LOCAL

Poor

Over: LITTLE BEAVER CREEK

080253504, Polk, IA

Built 1926 Load: 9.8 t ADT: 199

FM

Poor

Over: DEER CREEK

080231812, Polk, IA

Built 1950 Load: 10.1 t ADT: 2,421

LOCAL ROAD

Poor

Over: INDIAN CREEK

081220203, Polk, IA

Built 1916 Load: 10.2 t ADT: 45

LOCAL ROAD

Poor

Over: MUD CREEK

078222706, Polk, IA

Built 1913 Load: 12.6 t ADT: 79

WALNUT ST

Poor

Over: DES MOINES RIVER

078240400, Polk, IA

Built 1911 Load: 12.9 t ADT: 3,844

FM

Poor

Over: CREEK

080222605, Polk, IA

Built 1951 Load: 13.3 t ADT: 229

PRIVATE (SDB)

Poor

Over: STREAM (SDB)

079222604, Polk, IA

Built 1950 Load: 14.0 t ADT: 10

LOCAL ROAD

Poor

Over: CAMP CREEK

078221403, Polk, IA

Built 1914 Load: 14.1 t ADT: 26

LOCAL ROAD

Poor

Over: SKUNK RIVER

081231001, Polk, IA

Built 1928 Load: 14.2 t ADT: 29

ST JOHNS RD

Poor

Over: DRAINAGE

078240700, Polk, IA

Built 1900 Load: 14.6 t ADT: 684

FM

Poor

Over: BRANCH SKUNK RIVER

081231303, Polk, IA

Built 1968 Load: 14.8 t ADT: 131

GRANT ST SOUTH

Poor

Over: MUD CREEK

079220602, Polk, IA

Built 1927 Load: 15.1 t ADT: 2,902

LOCAL

Poor

Over: OVER UPRR

079230508, Polk, IA

Built 1948 Load: 16.3 t ADT: 399

FM

Poor

Over: CAMP CREEK

079222604, Polk, IA

Built 1950 Load: 17.3 t ADT: 459

FM

Poor

Over: TURKEY CREEK

081251401, Polk, IA

Built 1980 Load: 18.1 t ADT: 50

LOCAL

Poor

Over: MUD CREEK

077220201, Polk, IA

Built 1920 Load: 19.2 t ADT: 50

LOCAL

Poor

Over: CAMP CREEK

079223503, Polk, IA

Built 1959 Load: 19.6 t ADT: 34

FLEUR DR

Poor

Over: RACCOON AND RR

078240800, Polk, IA

Built 1936 Load: 20.9 t ADT: 2,825

YELLOW BANKS PK

Poor

Over: STREAM

078232301, Polk, IA

Built 1980 Load: 20.9 t

LOCAL ROAD

Poor

Over: LITTLE CREEK

081250501, Polk, IA

Built 1917 Load: 21.2 t ADT: 80

LOCAL

Poor

Over: CAMP CREEK

078222408, Polk, IA

Built 1930 Load: 23.2 t ADT: 79

LOCAL ROAD

Poor

Over: CREEK

078222801, Polk, IA

Built 1962 Load: 23.2 t ADT: 159

SE 6TH ST

Poor

Over: DES MOINES RIVER

000000000, Polk, IA

Built 1976 Load: 25.4 t ADT: 7,911

FLEUR DR

Poor

Over: OLD UP RR & SW 22ND

078241700, Polk, IA

Built 1936 Load: 29.3 t ADT: 15,634

SW 9TH ST

Poor

Over: CHERRY RR MLK PKWY

078240900, Polk, IA

Built 1967 Load: 32.2 t ADT: 14,108

SE 45TH ST

Poor

Over: OVER UP RR

078232900, Polk, IA

Built 1962 Load: 32.7 t ADT: 148

LOCAL ROAD

Poor

Over: MUD CREEK

078220503, Polk, IA

Built 1925 Load: 32.7 t ADT: 20

SE 5TH ST

Poor

Over: YEADER CREEK

078242700, Polk, IA

Built 1976 Load: 33.6 t ADT: 4,717

SW 8TH ST

Poor

Over: RR CHERRY MLK JR PKWY

078240900, Polk, IA

Built 1967 Load: 33.9 t ADT: 6,875

LOCAL ROAD

Poor

Over: DRAINAGE DITCH

080230902, Polk, IA

Built 1914 Load: 37.2 t ADT: 459

SW 9TH ST

Poor

Over: RACCOON RIVER & TRAIL

078240900, Polk, IA

Built 1967 Load: 41.7 t ADT: 12,809

WILLIAMS ST

Poor

Over: FOUR MILE CREEK

079233302, Polk, IA

Built 1978 Load: 42.4 t ADT: 3,908

Read our methodology - how this data is sourced, computed, and verified.

Related

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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.