County profile · official public datasets

Story County, IA

296 public highway bridges tracked in the FHWA National Bridge Inventory: 33.1% rated Good, 53% Fair, 13.9% Poor.

296
Public bridges: 33.1%
Good condition: 13.9%
Poor condition

The verdict

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

Story County pairs a better-than-median Poor-condition share among rated counties in the state with an older average build year than the state inventory.

Top 30%
lowest Poor share in state: 13.9%
Poor-condition share: 296
public highway bridges: 1968
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.

Story County Bridge Snapshot

According to the Federal Highway Administration's 2024 National Bridge Inventory, Story County ranks #30 of 99 Iowa counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 13.9%). Story County, Iowa contains 296 public highway bridges. Roughly 33.1% are rated “Good,” 53% “Fair,” and 13.9% “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

296

Public highway bridges in Story County

Good condition

33.1%

98 of 296 rated 7-9

Fair condition

53%

157 of 296 rated 5-6

Poor condition

13.9%

41 of 296 rated 4 or below

In-state Poor-share rank

#30 of 99

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

Condition distribution

Share of 296 NBI-tracked bridges by lowest applicable component rating.

Good

33.1% (98)

Fair

53% (157)

Poor

13.9% (41)

Story County's Poor-condition bridges carry 4,593 vehicle crossings a day

That is 0.5% of the county's reported daily bridge traffic on 13.9% of its bridges: Poor-condition structures carry less traffic than their share of the inventory. Each Poor bridge averages 112 crossings a day against 3,682 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 296 of 296 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.

63.9% of Story County's bridges have passed the 50-year mark

189 of the 296 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 33.1% 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 22.4% of the county's Poor-condition bridge traffic

E15/115TH ST over LONG DICK CREEK, built 1964, carries 1,028 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 41-bridge count understates how much of the daily burden sits on a single crossing.

Share is of the 4,593 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.

pre-1900

1
1900s

14
1910s

17
1920s

10
1930s

15
1940s

9
1950s

26
1960s

71
1970s

37
1980s

18
1990s

16
2000s

19
2010s

34
2020s

9

What this shows Construction peaked in the 1960s, when 71 of the county's bridges still in the inventory were built, which is 24% of those with a recorded year. That cohort is now 55 to 64 years old in the 2024 inventory. Its average build year is 1968, 11 years older than the Iowa average of 1979.

How Story County compares with Iowa's closest counties by inventory size

The 5 Iowa counties nearest Story County in number of bridges, with their condition splits. Its 13.9% Poor share is the 4th-lowest of these 6. Its average build year of 1968 against a peer-group mean of 1980 is 12 years older.

Showing the 5 closest of 98 Iowa counties eligible for comparison.

Bridge inventory size and condition shares for Story County and the 5 Iowa counties closest to it in inventory size
County	Bridges	Good	Fair	Poor	Avg. built
Cedar County	301	42.9%	37.5%	19.6%	1983
Crawford County	301	42.5%	48.5%	9%	1982
Story County (this page)	296	33.1%	53%	13.9%	1968
Cass County	295	25.4%	41%	33.6%	1976
Delaware County	293	39.2%	53.9%	6.8%	1981
Scott County	291	34.7%	55%	10.3%	1980

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 Story 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 Story County, both outside Iowa so the neighborhoods are not the same-state size table above.

Similar inventory size

Nearest county inventories outside IA (296 bridges here).

Marion County, IL · 296 bridges
Vigo County, IN · 296 bridges
Guadalupe County, TX · 296 bridges
Clark County, WI · 296 bridges

Similar average build year

Nearest mean year-built outside IA (1968 here).

Montgomery County, PA · avg 1968 · 828 bridges
San Joaquin County, CA · avg 1968 · 644 bridges
Providence County, RI · avg 1968 · 476 bridges
Imperial County, CA · avg 1968 · 444 bridges

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

All 296 Good 98 Fair 157 Poor 41

Fair-condition bridges (157)

Sort:

Story County Bridge Snapshot

Condition distribution

Story County's Poor-condition bridges carry 4,593 vehicle crossings a day

63.9% of Story County's bridges have passed the 50-year mark

One structure carries 22.4% of the county's Poor-condition bridge traffic

How Story County compares with Iowa'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 (157)

FIELD ENTRANCE

213TH ST

640TH AVE

320TH ST

100TH ST

710TH AVE

270TH ST

180TH ST

610TH AVE

170TH ST

567TH AVE

550TH AVE

730TH AVE

140TH ST

720TH AVE

730TH AVE

310TH ST

300TH ST

630TH AVE

120TH ST

US 30 WB TO I35 NB

630TH AVE

110TH ST

325TH ST

720TH AVE

150TH ST

SECOND ST

550TH AVE

120TH ST

MAIN ST

UNIVERSITY BLVD

CENTER ST

270TH ST

730TH AVE

140TH ST

MATHEWS ST

270TH ST

520TH AVE

PLEASANT VALLEY

530TH AVE

210TH ST

260TH ST

100TH ST

100TH ST

260TH ST

680TH AVE

322ND ST

295TH ST

315TH ST

550TH AVE

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