County profile · official public datasets

Boone County, IA

135 public highway bridges tracked in the FHWA National Bridge Inventory: 27.4% rated Good, 43% Fair, 29.6% Poor.

135
Public bridges
27.4%
Good condition
29.6%
Poor condition

The verdict

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

Boone 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.

79th
of 99 on Poor share
29.6%
Poor-condition share
135
public highway bridges
1955
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.

Boone County Bridge Snapshot

According to the Federal Highway Administration's 2024 National Bridge Inventory, Boone County ranks #79 of 99 Iowa counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 29.6%). Boone County, Iowa contains 135 public highway bridges. Roughly 27.4% are rated “Good,” 43% “Fair,” and 29.6% “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

135

Public highway bridges in Boone County

Good condition

27.4%

37 of 135 rated 7-9

Fair condition

43%

58 of 135 rated 5-6

Poor condition

29.6%

40 of 135 rated 4 or below

In-state Poor-share rank

#79 of 99

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

Condition distribution

Share of 135 NBI-tracked bridges by lowest applicable component rating.

Good
27.4% (37)
Fair
43% (58)
Poor
29.6% (40)

Boone County's Poor-condition bridges carry 3,048 vehicle crossings a day

That is 2.8% of the county's reported daily bridge traffic on 30.3% of its bridges: Poor-condition structures carry less traffic than their share of the inventory. Each Poor bridge averages 76 crossings a day against 919 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 132 of 135 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.

66.7% of Boone County's bridges have passed the 50-year mark

90 of the 135 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 27.4% 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 25.2% of the county's Poor-condition bridge traffic

FM over DES MOINES RIVER, built 1972, carries 769 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 40-bridge count understates how much of the daily burden sits on a single crossing.

Share is of the 3,048 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.

When Boone County's bridges were built

135 bridges with a recorded construction year, grouped by decade

bridges

What this shows Construction peaked in the 1900s, when 21 of the county's bridges still in the inventory were built, which is 15.6% of those with a recorded year. That cohort is now 115 to 124 years old in the 2024 inventory. Its average build year is 1955, 24 years older than the Iowa average of 1979.

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

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

The 5 Iowa counties nearest Boone County in number of bridges, with their condition splits. Its 29.6% Poor share is the 6th-lowest of these 6. Its average build year of 1955 against a peer-group mean of 1978 is 23 years older.

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

Bridge inventory size and condition shares for Boone County and the 5 Iowa counties closest to it in inventory size
County Bridges Poor
Clay County 151 9.9%
Muscatine County 144 21.5%
Hancock County 138 20.3%
Palo Alto County 135 18.5%
Boone County (this page) 135 29.6%
Monroe County 130 24.6%

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

Similar inventory size

Nearest county inventories outside IA (135 bridges here).

Similar average build year

Nearest mean year-built outside IA (1955 here).

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

All 135 Good 37 Fair 58 Poor 40

Good-condition bridges (37)

US 30 & 169

Good

Over: EAST BEAVER CREEK

1.2 MI. W OF E JCT US 169, Boone, IA

Built 1962 Load: 18.1 t ADT: 5,900

US 169

Good

Over: STREAM

4.7 MI. S OF S JCT. US 30, Boone, IA

Built 1935 Load: 18.1 t ADT: 3,370

IA 210

Good

Over: STREAM

IN MADRID, Boone, IA

Built 1989 Load: 20.0 t ADT: 2,880

190TH ST

Good

Over: TRIB OF BEAVER CREEK

084282201, Boone, IA

Built 2016 Load: 25.3 t ADT: 34

R AVE

Good

Over: PRAIRIE CREEK

085263602, Boone, IA

Built 2017 Load: 25.3 t ADT: 20

US 169

Good

Over: LITTLE BEAVER CREEK

4.6 MILES NORTH OF IA 141, Boone, IA

Built 1984 Load: 28.8 t ADT: 3,370

US 169

Good

Over: MIDDLE BEAVER CREEK

1.5 MI N OF W JCT US 30, Boone, IA

Built 1932 Load: 29.8 t ADT: 1,890

MONTONA RD

Good

Over: HONEY CREEK

083260714, Boone, IA

Built 2017 Load: 32.4 t ADT: 110

140TH ST

Good

Over: IOWAY CREEK

085252701, Boone, IA

Built 2016 Load: 32.4 t ADT: 30

U AVE

Good

Over: MONTGOMERY CREEK

085253302, Boone, IA

Built 2019 Load: 32.4 t ADT: 30

IA 17

Good

Over: UP RR & 210TH ST

1.2 MI. N. OF US 30, Boone, IA

Built 2021 Load: 32.4 t ADT: 1,640

E 41

Good

Over: DES MOINES RIVER

084273607, Boone, IA

Built 2000 Load: 32.7 t ADT: 1,526

A AVE

Good

Over: STREAM

084280702, Boone, IA

Built 2019 Load: 32.7 t ADT: 5

LOCAL

Good

Over: IOWAY CREEK

085251603, Boone, IA

Built 2006 Load: 33.7 t ADT: 26

E26 170TH ST

Good

Over: BEAVER CREEK

084280901, Boone, IA

Built 2016 Load: 34.3 t ADT: 359

US 30

Good

Over: MIDDLE BEAVER CREEK

0.5 MI. W OF W JCT US 169, Boone, IA

Built 2016 Load: 34.7 t ADT: 3,950

FM

Good

Over: BLUFF CREEK

085272902, Boone, IA

Built 1987 Load: 36.3 t ADT: 977

LOCAL

Good

Over: BEAVER CREEK

083282801, Boone, IA

Built 1999 Load: 39.0 t ADT: 15

335TH ST

Good

Over: LITTLE BEAVER CREEK

082273305, Boone, IA

Built 2011 Load: 40.2 t ADT: 40

W AVE

Good

Over: MONTGOMERY CREEK

085253502, Boone, IA

Built 2015 Load: 40.2 t ADT: 30

FM

Good

Over: BEAVER CREEK

083282101, Boone, IA

Built 2010 Load: 41.5 t ADT: 20

LOCAL

Good

Over: BEAVER CREEK

082282706, Boone, IA

Built 1996 Load: 42.3 t ADT: 60

LOWER LEDGES RD

Good

Over: PEASE CREEK

IN LEDGES STATE PARK, Boone, IA

Built 2011 Load: 42.3 t

LOCAL

Good

Over: BEAVER CREEK

082281505, Boone, IA

Built 1997 Load: 42.5 t ADT: 34

FM

Good

Over: IOWAY CREEK

084251201, Boone, IA

Built 2002 Load: 42.5 t ADT: 170

180TH ST

Good

Over: BEAVER CREEK

084281601, Boone, IA

Built 2020 Load: 42.8 t ADT: 71

240TH ST

Good

Over: MIDDLE BEAVER CREEK

083281601, Boone, IA

Built 2021 Load: 48.0 t ADT: 26

FM

Good

Over: ELKHORN CREEK

085273603, Boone, IA

Built 1997 Load: 48.0 t ADT: 71

LOCAL

Good

Over: BIG CREEK

082251603, Boone, IA

Built 2004 Load: 48.2 t ADT: 30

LOCAL

Good

Over: EVERSOLL CREEK

082262101, Boone, IA

Built 2009 Load: 48.2 t ADT: 30

LOCAL

Good

Over: LITTLE BEAVER CREEK

082272901, Boone, IA

Built 2004 Load: 48.2 t ADT: 45

FM

Good

Over: LITTLE BEAVER CREEK

082273201, Boone, IA

Built 2003 Load: 48.2 t ADT: 40

US 30

Good

Over: BEAVER CREEK

1.1 mi. W of Jct. SR P54, Boone, IA

Built 2008 Load: 52.3 t ADT: 3,950

LOCAL

Good

Over: BEAVER CREEK

083280701, Boone, IA

Built 2007 Load: 52.9 t ADT: 15

LOCAL

Good

Over: BEAVER CREEK

083281801, Boone, IA

Built 2004 Load: 52.9 t ADT: 26

110TH ST

Good

Over: TRIB OF SQUAW CREEK

085251001, Boone, IA

Built 2018 Load: 55.7 t ADT: 30

IA 17

Good

Over: BRANCH SQUAW CREEK

1.8 MILES N OF JCT SR E18, Boone, IA

Built 1979 Load: 88.1 t ADT: 2,260

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.