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

Good-condition bridges (315)

WESTOWN PARKWAY

Good

Over: I-80/I-35

0.2 mi. E of I-235, Polk, IA

Built 1997 Load: 38.0 t ADT: 12,526

M LUTHER KING

Good

Over: I-235

3.2 MILES E OF JCT IA 28, Polk, IA

Built 2003 Load: 38.0 t ADT: 10,548

SB US 65

Good

Over: EAST OAKWOOD DRIVE

0.4 MILES S OF JCT IA 163, Polk, IA

Built 1997 Load: 38.1 t ADT: 8,300

50TH ST-ST FARM

Good

Over: I-235

0.3 mi. E of W Jct. I-235, Polk, IA

Built 2000 Load: 38.4 t ADT: 18,366

EB I-235

Good

Over: 73RD ST& IA INTERSTATE R

3.2 MI E OF W JCT I 80/35, Polk, IA

Built 1968 Load: 38.4 t ADT: 50,400

FM

Good

Over: MUD CREEK

079222901, Polk, IA

Built 1986 Load: 38.4 t ADT: 278

W 1ST STREET

Good

Over: ROCK CREEK

080242105, Polk, IA

Built 2007 Load: 38.8 t ADT: 4,709

NB I-35/EB I-80

Good

Over: IA 28

At jct. IA 28, Polk, IA

Built 1999 Load: 38.9 t ADT: 39,100

NB US 65

Good

Over: I-80

AT WEST JUNCTION I-80, Polk, IA

Built 1992 Load: 38.9 t ADT: 7,600

I-80 EB RAMP D

Good

Over: DRAINAGE

0.2 MILE EAST OF US 69, Polk, IA

Built 1999 Load: 38.9 t ADT: 2,300

US 65 SB

Good

Over: VANDALIA ROAD & BNSF RR

2.4 MILES S OF JCT IA 163, Polk, IA

Built 1997 Load: 39.0 t ADT: 11,350

NB US 65

Good

Over: VANDALIA RD (BP)

2.1 MILES S OF JCT IA 163, Polk, IA

Built 1997 Load: 39.7 t ADT: 11,350

NW 13TH ST

Good

Over: ROCK CREEK

080241601, Polk, IA

Built 2016 Load: 40.2 t ADT: 95

GRAND AVE

Good

Over: JORDAN CREEK

City of West Des Moines, Polk, IA

Built 2015 Load: 40.2 t ADT: 3,865

PLEASANT DR

Good

Over: CUMMINS CREEK

078250200, Polk, IA

Built 2010 Load: 40.5 t ADT: 1,127

NB US 65

Good

Over: DRAINAGE DITCH

4.4 MILES N OF N JCT I-80, Polk, IA

Built 1979 Load: 40.5 t ADT: 8,200

NW 128TH ST SB

Good

Over: WALNUT CREEK

079253200, Polk, IA

Built 1998 Load: 40.5 t ADT: 7,065

NW 128TH ST NB

Good

Over: WALNUT CREEK

079253200, Polk, IA

Built 2007 Load: 40.5 t ADT: 6,875

5TH AVE

Good

Over: I-235

4.2 mi. E of Jct. IA #28, Polk, IA

Built 2003 Load: 40.8 t ADT: 3,120

EB IA 163

Good

Over: CAMP CREEK

6.9 mi. E of Jct. US 65, Polk, IA

Built 2007 Load: 40.9 t ADT: 6,300

WB IA 163

Good

Over: CAMP CREEK

6.9 mi. E of Jct. U.S. 65, Polk, IA

Built 2007 Load: 40.9 t ADT: 6,300

NE 36TH

Good

Over: OTTER CREEK

080230700, Polk, IA

Built 1982 Load: 40.9 t ADT: 6,694

NB I-35

Good

Over: RACCOON RIVER

0.6 mi. N of Jct. Iowa #5, Polk, IA

Built 2002 Load: 41.1 t ADT: 28,800

9TH STREET

Good

Over: I-235

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

Built 2007 Load: 41.5 t ADT: 5,534

SB US 65

Good

Over: IA 5

AT N JCT. OF IA 5, Polk, IA

Built 1997 Load: 41.6 t ADT: 8,900

WB I-235

Good

Over: 17TH ST

1.3 mi. W of Jct. IA 28, Polk, IA

Built 1967 Load: 41.8 t ADT: 56,600

FM

Good

Over: FOUR MILE CREEK

079231701, Polk, IA

Built 1991 Load: 42.1 t ADT: 1,504

COWLES DRIVE

Good

Over: GARAGE ENTRY LANE

0.3 mi. N of Entrance, Polk, IA

Built 2023 Load: 42.1 t

MEREDITH DR

Good

Over: I-35 AND I-80

0.4 mi. W of Jct. IA 141, Polk, IA

Built 2006 Load: 42.3 t ADT: 12,055

E 6TH ST

Good

Over: I-235

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

Built 2002 Load: 42.3 t ADT: 5,300

EAST LOCUST ST

Good

Over: DES MOINES RIVER

078240400, Polk, IA

Built 2020 Load: 42.4 t ADT: 6,029

S 35TH STREET

Good

Over: IA 5

1.6 mi. E of Jct. I-35, Polk, IA

Built 2002 Load: 42.4 t ADT: 1,414

EB I-235

Good

Over: UP RR

1.3 MILES E OF JCT US 6, Polk, IA

Built 2006 Load: 42.9 t ADT: 25,550

NW 70TH AVENUE

Good

Over: BEAVER CREEK

000000000, Polk, IA

Built 1994 Load: 43.1 t ADT: 5,205

UNIVSITY RAMP A

Good

Over: UPRR

0.2 MILES E OF JCT IA 163, Polk, IA

Built 2001 Load: 43.1 t ADT: 2,300

VANDALIA RD

Good

Over: DRAINAGE

078231600, Polk, IA

Built 2020 Load: 43.1 t ADT: 6,300

EB I-235

Good

Over: 28TH STREET

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

Built 2004 Load: 43.4 t ADT: 55,350

IA 5 SB

Good

Over: 8TH STREET

1.6 MILES NW JUNCT IA 28, Polk, IA

Built 2002 Load: 43.4 t ADT: 15,050

EB I-235

Good

Over: NB I-35 & EB I-80

AT EAST JUNCTION I-35/80, Polk, IA

Built 2007 Load: 43.4 t ADT: 21,050

E 9TH STREET

Good

Over: I-235

5.1 mi. E of Jct. IA #28, Polk, IA

Built 2001 Load: 43.5 t ADT: 1,723

WB I-235

Good

Over: 35TH STREET

2.1 mi. E of Jct. IA #28, Polk, IA

Built 2005 Load: 43.5 t ADT: 55,350

EB I-235 RAMP

Good

Over: KEO WAY RAMP TO EB I-235

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

Built 2005 Load: 43.7 t ADT: 11,900

SW CONNECTOR

Good

Over: IA 5

2.3 MILES N OF JCT IA 28, Polk, IA

Built 2002 Load: 43.8 t ADT: 1,079

NE 72ND ST

Good

Over: I-80 & US 6

1.6 mi. E of Jct. U.S. 65, Polk, IA

Built 2006 Load: 43.9 t ADT: 5,975

IA 415

Good

Over: ROCK CREEK

1.9 MILES N OF JCT IA 160, Polk, IA

Built 1993 Load: 43.9 t ADT: 9,100

DOUGLAS AVE

Good

Over: I 35 & I 80

At JUNCTION I-80 & I-35, Polk, IA

Built 2002 Load: 44.0 t ADT: 8,570

WB I-235

Good

Over: UP RR

1.3 MILES E OF JCT US 6, Polk, IA

Built 2006 Load: 44.1 t ADT: 25,550

VALLEY WEST DR

Good

Over: I 235

1.3 MI E OF W JCT 80/35, Polk, IA

Built 2003 Load: 44.3 t ADT: 8,664

FM

Good

Over: DES MOINES RIVER

NW 66th over Des Moines, Polk, IA

Built 2016 Load: 44.4 t ADT: 11,354

NE 150TH AVE

Good

Over: SKUNK RIVER

081231401, Polk, IA

Built 2012 Load: 44.4 t ADT: 142

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.