County profile · official public datasets

Linn County, IA

506 public highway bridges tracked in the FHWA National Bridge Inventory: 46.4% rated Good, 47.2% Fair, 6.3% Poor.

506
Public bridges
46.4%
Good condition
6.3%
Poor condition

The verdict

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

Linn 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 6%
lowest Poor share in state
6.3%
Poor-condition share
506
public highway bridges
1987
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.

Linn County Bridge Snapshot

According to the Federal Highway Administration's 2024 National Bridge Inventory, Linn County ranks #6 of 99 Iowa counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 6.3%). Linn County, Iowa contains 506 public highway bridges. Roughly 46.4% are rated “Good,” 47.2% “Fair,” and 6.3% “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

506

Public highway bridges in Linn County

Good condition

46.4%

235 of 506 rated 7-9

Fair condition

47.2%

239 of 506 rated 5-6

Poor condition

6.3%

32 of 506 rated 4 or below

In-state Poor-share rank

#6 of 99

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

Condition distribution

Share of 506 NBI-tracked bridges by lowest applicable component rating.

Good
46.4% (235)
Fair
47.2% (239)
Poor
6.3% (32)

Linn County's Poor-condition bridges carry 80,824 vehicle crossings a day

That is 3.1% 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 2,526 crossings a day against 2,954 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 505 of 506 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.

20.2% of Linn County's bridges have passed the 50-year mark

102 of the 506 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 46.4% 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 13.3% of the county's Poor-condition bridge traffic

8TH AVE over INDIAN CREEK, built 1988, carries 10,789 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 32-bridge count understates how much of the daily burden sits on a single crossing.

Share is of the 80,824 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.

When Linn County's bridges were built

506 bridges with a recorded construction year, grouped by decade

bridges

What this shows Construction peaked in the 1970s, when 96 of the county's bridges still in the inventory were built, which is 19% of those with a recorded year. That cohort is now 45 to 54 years old in the 2024 inventory. Its average build year is 1987, 8 years newer than the Iowa average of 1979.

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

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

The 5 Iowa counties nearest Linn County in number of bridges, with their condition splits. Its 6.3% Poor share is the 2nd-lowest of these 6. Its average build year of 1987 against a peer-group mean of 1983 is in line with the group.

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

Bridge inventory size and condition shares for Linn County and the 5 Iowa counties closest to it in inventory size
County Bridges Poor
Pottawattamie County 557 9.3%
Polk County 545 6.4%
Linn County (this page) 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 Linn 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 Linn County, both outside Iowa so the neighborhoods are not the same-state size table above.

Similar inventory size

Nearest county inventories outside IA (506 bridges here).

Similar average build year

Nearest mean year-built outside IA (1987 here).

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

All 506 Good 235 Fair 239 Poor 32

Good-condition bridges (235)

PRAIRIE MAIN RD

Good

Over: CEDAR CREEK

086052905, Linn, IA

Built 2000 Load: 57.9 t ADT: 88

HEATONS VALLEY

Good

Over: TRIB TO HEATONS CREEK

086062303, Linn, IA

Built 1997 Load: 57.9 t ADT: 59

FORD RD

Good

Over: HEATONS CREEK

086063504, Linn, IA

Built 2002 Load: 57.9 t ADT: 59

CAMPFIRE RD

Good

Over: TRIB TO WAPSIPINICON R

086071703, Linn, IA

Built 1997 Load: 57.9 t ADT: 88

WEST OTTER RD

Good

Over: W OTTER CREEK

086073002, Linn, IA

Built 1999 Load: 57.9 t ADT: 29

JUSTINS RD

Good

Over: JUSTINS CREEK

086073603, Linn, IA

Built 2000 Load: 57.9 t ADT: 26

BETTYS GROVE RD

Good

Over: E BLUE CREEK

086081502, Linn, IA

Built 2001 Load: 57.9 t ADT: 128

BETTYS GROVE RD

Good

Over: EAST BLUE CREEK

086082202, Linn, IA

Built 2001 Load: 57.9 t ADT: 10

WILEYS RD

Good

Over: W OTTER CREEK

086082401, Linn, IA

Built 2001 Load: 57.9 t ADT: 49

RING RD

Good

Over: E BLUE CREEK

086082803, Linn, IA

Built 2001 Load: 57.9 t ADT: 29

RING RD

Good

Over: EAST BLUE CREEK

086082808, Linn, IA

Built 2003 Load: 57.9 t ADT: 29

FEE RD

Good

Over: E BLUE CREEK

086083307, Linn, IA

Built 2007 Load: 57.9 t ADT: 70

GRUBBS CR RD

Good

Over: CRUBB CREEK

086083405, Linn, IA

Built 1997 Load: 57.9 t ADT: 70

UP.BOULDER RD

Good

Over: BISON CREEK

086051803, Linn, IA

Built 1995 Load: 57.9 t ADT: 29

UPPER BOULDER R

Good

Over: SILVER CREEK

086051401, Linn, IA

Built 1998 Load: 57.9 t ADT: 11

MORGAN BR RD

Good

Over: MORGAN CREEK

083082802, Linn, IA

Built 2000 Load: 57.9 t ADT: 34

ALDERMAN RD

Good

Over: LITTLE BIG CREEK

084051502, Linn, IA

Built 2000 Load: 57.9 t ADT: 59

PARIS RD

Good

Over: EAST OTTER CREEK

086072701, Linn, IA

Built 2000 Load: 57.9 t ADT: 216

NORTH MARION RD

Good

Over: DRY CREEK

085060702, Linn, IA

Built 2001 Load: 57.9 t ADT: 44

76TH AVE SW

Good

Over: TISSLE HOLLOW CREEK

Linn # 1182, Linn, IA

Built 2010 Load: 57.9 t ADT: 137

MIDWAY RD

Good

Over: E OTTER CR

084070705, Linn, IA

Built 2005 Load: 58.0 t ADT: 255

ALBURNETT RD

Good

Over: DRY CREEK

085073608, Linn, IA

Built 1996 Load: 58.3 t ADT: 1,895

ROWLEY ST

Good

Over: DRAINAGE

000000000, Linn, IA

Built 2005 Load: 59.1 t ADT: 243

WILLOW CR.RD.

Good

Over: WILLOW CREEK

082051604, Linn, IA

Built 1996 Load: 59.1 t ADT: 39

AUSTIN RD

Good

Over: E INDIAN CREEK

084060401, Linn, IA

Built 1994 Load: 59.1 t ADT: 90

US 30

Good

Over: DRAINAGE

1.4 mi. E US30/IA1 INTCHG, Linn, IA

Built 2018 Load: 60.3 t ADT: 5,400

LINN BENTON RD

Good

Over: BR OF BLUE CREEK

086081802, Linn, IA

Built 2018 Load: 63.2 t ADT: 25

W BLUE RD

Good

Over: WEST BLUE CREEK

W Blue Rd T86N R8W 30, Linn, IA

Built 2010 Load: 65.4 t ADT: 70

SILVER CK RD

Good

Over: TRIB TO SILVER CREEK

086052401, Linn, IA

Built 2002 Load: 91.7 t ADT: 15

LISBON BLVD

Good

Over: SPRING CREEK

0.4miNjctUS30&LisbonBLVD, Linn, IA

Built 2017 Load: 97.2 t ADT: 786

FLEMINGVIL RD

Good

Over: EAST OTTER CREEK

085071006, Linn, IA

Built 1995 Load: 99.9 t ADT: 70

NELSON CK RD

Good

Over: NELSON CR

085082703, Linn, IA

Built 2003 Load: 99.9 t ADT: 39

INDIAN BRIDGE RD

Good

Over: EAST INDIAN CREEK

085063401, Linn, IA

Built 2001 Load: 99.9 t ADT: 20

FROZEN HILL RD

Good

Over: TRIB TO BUFFALO CREEK

085051202, Linn, IA

Built 2008 Load: 99.9 t ADT: 39

33RD AVE SW

Good

Over: UNNAMED TRIBUTARY

000000000, Linn, IA

Built 2006 Load: 99.9 t ADT: 10,700

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.