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

Poor-condition bridges (40)

FM

Poor

Over: DES MOINES RIVER

084272705, Boone, IA

Built 1909 Load: 0.0 t ADT: 80

LOCAL

Poor

Over: TRIB DES MOINES RIVER

084273103, Boone, IA

Built 1900 Load: 0.0 t ADT: 26

LOCAL

Poor

Over: TRIB DES MOINES RIVER

085271404, Boone, IA

Built 1900 Load: 0.0 t ADT: 20

FM

Poor

Over: LITTLE BEAVER CREEK

082273302, Boone, IA

Built 1973 Load: 3.3 t ADT: 45

LOCAL

Poor

Over: BEAVER CREEK

082280304, Boone, IA

Built 1915 Load: 3.6 t ADT: 20

FIELD ENTRANCE

Poor

Over: TRIB DES MOINES RIVER

084272305, Boone, IA

Built 1900 Load: 3.8 t ADT: 40

LOCAL

Poor

Over: BLUFF CREEK

084270904, Boone, IA

Built 1900 Load: 5.7 t ADT: 20

190TH ST

Poor

Over: STREAM

084282102, Boone, IA

Built 1900 Load: 9.1 t ADT: 20

160TH ST

Poor

Over: BEAVER CREEK

084280401, Boone, IA

Built 1915 Load: 10.5 t ADT: 5

LOCAL

Poor

Over: BEAVER CREEK

083280901, Boone, IA

Built 1900 Load: 11.3 t ADT: 26

LOCAL

Poor

Over: BIG CREEK

082252701, Boone, IA

Built 1917 Load: 12.4 t ADT: 30

FM

Poor

Over: BLUFF CREEK

085273101, Boone, IA

Built 1915 Load: 12.6 t ADT: 50

LOCAL

Poor

Over: MONTGOMERY CREEK

085262501, Boone, IA

Built 1900 Load: 13.6 t ADT: 34

FM

Poor

Over: BR IOWAY CREEK

085250403, Boone, IA

Built 1916 Load: 13.9 t ADT: 20

FM

Poor

Over: BLUFF CREEK

085272001, Boone, IA

Built 1957 Load: 14.2 t ADT: 718

LOCAL

Poor

Over: DES MOINES RIVER

082260305, Boone, IA

Built 1930 Load: 15.3 t ADT: 34

LOCAL

Poor

Over: LITTLE BEAVER CREEK

082273308, Boone, IA

Built 1939 Load: 16.1 t ADT: 26

LOCAL

Poor

Over: BIG CREEK

082252902, Boone, IA

Built 1900 Load: 16.3 t ADT: 90

LOCAL

Poor

Over: PRAIRIE CREEK

084250402, Boone, IA

Built 1915 Load: 16.3 t ADT: 30

LOCAL

Poor

Over: BEAVER CREEK

084282802, Boone, IA

Built 1900 Load: 17.3 t ADT: 11

LOCAL

Poor

Over: SQUAW CREEK

085252501, Boone, IA

Built 1900 Load: 17.8 t ADT: 15

LOCAL

Poor

Over: BEAVER CREEK

084283301, Boone, IA

Built 1920 Load: 18.0 t ADT: 20

LOCAL

Poor

Over: BEAVER CREEK

084282701, Boone, IA

Built 1920 Load: 18.3 t ADT: 20

LOCAL

Poor

Over: TRIB.DES MOINES RIVER

084272203, Boone, IA

Built 1900 Load: 18.4 t ADT: 71

LOCAL

Poor

Over: LITTLE BEAVER CREEK

082272802, Boone, IA

Built 1900 Load: 19.9 t ADT: 26

FM

Poor

Over: IOWAY CREEK

085253501, Boone, IA

Built 1949 Load: 20.2 t ADT: 50

LOCAL

Poor

Over: MONTGOMERY CREEK

085253404, Boone, IA

Built 1915 Load: 20.4 t ADT: 15

LOCAL

Poor

Over: BIG CREEK

083261301, Boone, IA

Built 1915 Load: 22.6 t ADT: 26

LOCAL

Poor

Over: LITTLE BEAVER CREEK

082271901, Boone, IA

Built 1915 Load: 23.5 t ADT: 40

LOCAL

Poor

Over: BEAVER CREEK

084282901, Boone, IA

Built 1915 Load: 26.6 t ADT: 11

LOCAL

Poor

Over: BLUFF CREEK

085271701, Boone, IA

Built 1920 Load: 26.9 t ADT: 30

LOCAL

Poor

Over: ONION CREEK

084252502, Boone, IA

Built 1900 Load: 27.2 t ADT: 60

LOCAL

Poor

Over: BIG CREEK

083252901, Boone, IA

Built 1915 Load: 29.0 t ADT: 50

FM

Poor

Over: DES MOINES RIVER

083262905, Boone, IA

Built 1972 Load: 29.3 t ADT: 769

FM

Poor

Over: TRIBUTARY BEAVER CREEK

084283202, Boone, IA

Built 1962 Load: 29.9 t ADT: 80

FM

Poor

Over: TRIB. OF BEAVER CREEK

082280305, Boone, IA

Built 1948 Load: 30.3 t ADT: 279

LOCAL

Poor

Over: MONTGOMERY CREEK

085253102, Boone, IA

Built 1915 Load: 31.1 t ADT: 5

LOCAL

Poor

Over: IOWAY CREEK

085250902, Boone, IA

Built 1920 Load: 32.6 t ADT: 20

LOCAL

Poor

Over: BEAVER CREEK

083281101, Boone, IA

Built 1920 Load: 35.6 t ADT: 26

FM

Poor

Over: TRIB. OF SQUAW CREEK

085253601, Boone, IA

Built 1920 Load: 36.6 t ADT: 90

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.