County profile · official public datasets

Polk County, MO

185 public highway bridges tracked in the FHWA National Bridge Inventory: 31.9% rated Good, 47.6% Fair, 20.5% Poor.

185
Public bridges: 31.9%
Good condition: 20.5%
Poor condition

The verdict

According to the Federal Highway Administration's 2024 National Bridge Inventory.

Polk 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.

111th
of 115 on Poor share: 20.5%
Poor-condition share: 185
public highway bridges: 1966
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 #111 of 115 Missouri counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 20.5%). Polk County, Missouri contains 185 public highway bridges. Roughly 31.9% are rated “Good,” 47.6% “Fair,” and 20.5% “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

185

Public highway bridges in Polk County

Good condition

31.9%

59 of 185 rated 7-9

Fair condition

47.6%

88 of 185 rated 5-6

Poor condition

20.5%

38 of 185 rated 4 or below

In-state Poor-share rank

#111 of 115

Among Missouri counties with 5+ bridges, lower share ranks better

Condition distribution

Share of 185 NBI-tracked bridges by lowest applicable component rating.

Good

31.9% (59)

Fair

47.6% (88)

Poor

20.5% (38)

Polk County's Poor-condition bridges carry 30,556 vehicle crossings a day

That is 11.5% of the county's reported daily bridge traffic on 20.5% of its bridges: Poor-condition structures carry less traffic than their share of the inventory. Each Poor bridge averages 804 crossings a day against 921 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 185 of 185 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.

51.9% of Polk County's bridges have passed the 50-year mark

96 of the 185 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 31.9% 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 32.2% of the county's Poor-condition bridge traffic

MO 13 N over DRY SAC RVR, built 1970, carries 9,847 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 38-bridge count understates how much of the daily burden sits on a single crossing.

Share is of the 30,556 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.

1900s

38
1910s

1
1920s

12
1930s

5
1940s

8
1950s

12
1960s

12
1970s

10
1980s

4
1990s

16
2000s

33
2010s

25
2020s

9

What this shows Construction peaked in the 1900s, when 38 of the county's bridges still in the inventory were built, which is 20.5% of those with a recorded year. That cohort is now 115 to 124 years old in the 2024 inventory. Its average build year is 1966, 13 years older than the Missouri average of 1979.

How Polk County compares with Missouri's closest counties by inventory size

The 5 Missouri counties nearest Polk County in number of bridges, with their condition splits. Its 20.5% Poor share is the 6th-lowest of these 6. Its average build year of 1966 against a peer-group mean of 1980 is 14 years older.

Showing the 5 closest of 114 Missouri counties eligible for comparison.

Bridge inventory size and condition shares for Polk County and the 5 Missouri counties closest to it in inventory size
County	Bridges	Good	Fair	Poor	Avg. built
Grundy County	187	54%	34.8%	11.2%	1992
Marion County	186	37.1%	53.8%	9.1%	1977
Livingston County	185	34.1%	50.3%	15.7%	1978
Ray County	185	36.2%	51.4%	12.4%	1977
Polk County (this page)	185	31.9%	47.6%	20.5%	1966
Scott County	182	39.6%	53.8%	6.6%	1978

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 Missouri so the neighborhoods are not the same-state size table above.

Similar inventory size

Nearest county inventories outside MO (185 bridges here).

Chambers County, AL · 185 bridges
Maui County, HI · 185 bridges
Lawrence County, IL · 185 bridges
Saline County, IL · 185 bridges

Similar average build year

Nearest mean year-built outside MO (1966 here).

Butler County, KS · avg 1966 · 591 bridges
Grafton County, NH · avg 1966 · 544 bridges
Queens County, NY · avg 1966 · 514 bridges
Lehigh County, PA · avg 1966 · 381 bridges

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

All 185 Good 59 Fair 88 Poor 38

Fair-condition bridges (88)

Sort:

Polk County Bridge Snapshot

Condition distribution

Polk County's Poor-condition bridges carry 30,556 vehicle crossings a day

51.9% of Polk County's bridges have passed the 50-year mark

One structure carries 32.2% of the county's Poor-condition bridge traffic

How Polk County compares with Missouri's closest counties by inventory size

Nationwide counties with similar inventory size or average build year

Similar inventory size

Similar average build year

Fair-condition bridges (88)

COUNTY RD S-178

COUNTY RD 25

COUNTY RD E-387

COUNTY RD S-21

COUNTY RD S-28

COUNTY RD S-28

COUNTY RD E-560

COUNTY RD E-435

COUNTY RD S-196

COUNTY RD E-322

COUNTY RD S-75

COUNTY RD E-464

COUNTY RD S-225

COUNTY RD S-142

COUNTY RD S-60

RT K S

RT C E

RT J S

COUNTY RD S-24

COUNTY RD S-145

MO 123 S

MO 64 E

S MAIN ST

BENTON AVE

S LILLIAN AVE

MO 123 S

RT FF S

E-390TH RD

COUNTY RD S-86

MO 123 S

RT T E

RT O S

RT O S

MO 123 S

RT H S

RT W E

RT H S

MO 32 E

RT T E

MO 32 E

MO 123 S

RT D S

COUNTY RD S 200

562ND RD

RT W E

COUNTY RD E-405

RT AC E

COUNTY RD E-430

COUNTY RD S-225

COUNTY RD S-80

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