County profile · official public datasets

Linn County, OR

566 public highway bridges tracked in the FHWA National Bridge Inventory: 20.8% rated Good, 61.5% Fair, 17.7% Poor.

566
Public bridges: 20.8%
Good condition: 17.7%
Poor condition

The verdict

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

Linn County posts a higher-than-median Poor-condition share among rated counties in the state across large county bridge inventory.

36th
of 36 on Poor share: 17.7%
Poor-condition share: 566
public highway bridges: 1971
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 #36 of 36 Oregon counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 17.7%). Linn County, Oregon contains 566 public highway bridges. Roughly 20.8% are rated “Good,” 61.5% “Fair,” and 17.7% “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

566

Public highway bridges in Linn County

Good condition

20.8%

118 of 566 rated 7-9

Fair condition

61.5%

348 of 566 rated 5-6

Poor condition

17.7%

100 of 566 rated 4 or below

In-state Poor-share rank

#36 of 36

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

Condition distribution

Share of 566 NBI-tracked bridges by lowest applicable component rating.

Good

20.8% (118)

Fair

61.5% (348)

Poor

17.7% (100)

Linn County's Poor-condition bridges carry 80,207 vehicle crossings a day

That is 3.5% of the county's reported daily bridge traffic on 17.7% of its bridges: Poor-condition structures carry less traffic than their share of the inventory. Each Poor bridge averages 802 crossings a day against 2,136 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 566 of 566 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.

65.7% of Linn County's bridges have passed the 50-year mark

372 of the 566 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 20.8% 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 19% of the county's Poor-condition bridge traffic

US 20 (HWY 16) EB over Lebanon Ditch, built 1921, carries 15,212 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 100-bridge count understates how much of the daily burden sits on a single crossing.

Share is of the 80,207 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.

1920s

3
1930s

17
1940s

16
1950s

116
1960s

180
1970s

80
1980s

45
1990s

32
2000s

59
2010s

14
2020s

4

What this shows Construction peaked in the 1960s, when 180 of the county's bridges still in the inventory were built, which is 31.8% of those with a recorded year. That cohort is now 55 to 64 years old in the 2024 inventory. Its average build year (1971) matches the Oregon average (1975).

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

The 5 Oregon counties nearest Linn County in number of bridges, with their condition splits. Its 17.7% Poor share is the 6th-lowest of these 6. Its average build year of 1971 against a peer-group mean of 1972 is in line with the group.

Showing the 5 closest of 35 Oregon counties eligible for comparison.

Bridge inventory size and condition shares for Linn County and the 5 Oregon counties closest to it in inventory size
County	Bridges	Good	Fair	Poor	Avg. built
Douglas County	699	34%	62.8%	3.1%	1973
Linn County (this page)	566	20.8%	61.5%	17.7%	1971
Multnomah County	473	11.8%	85.2%	3%	1967
Jackson County	401	34.2%	64.3%	1.5%	1976
Marion County	373	21.2%	74.5%	4.3%	1971
Clackamas County	367	31.1%	66.5%	2.5%	1975

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

Similar inventory size

Nearest county inventories outside OR (566 bridges here).

York County, PA · 569 bridges
Shawnee County, KS · 563 bridges
Middlesex County, NJ · 563 bridges
Summit County, OH · 563 bridges

Similar average build year

Nearest mean year-built outside OR (1971 here).

Wayne County, MI · avg 1971 · 1,026 bridges
Baltimore County, MD · avg 1971 · 783 bridges
Washington County, PA · avg 1971 · 655 bridges
Monmouth County, NJ · avg 1971 · 505 bridges

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

All 566 Good 118 Fair 348 Poor 100

All bridges (566)

Sort:

Linn County Bridge Snapshot

Condition distribution

Linn County's Poor-condition bridges carry 80,207 vehicle crossings a day

65.7% of Linn County's bridges have passed the 50-year mark

One structure carries 19% of the county's Poor-condition bridge traffic

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

Nationwide counties with similar inventory size or average build year

Similar inventory size

Similar average build year

All bridges (566)

BOSTON MILL RD

First Ave

ROAD

GORE RD

CAMP MORRISON RD

COUNTY RD 601

OR 99E (HWY 58) NB

Ogle Road

Boston Mill Road

RICHARDSON GAP N.

QUARTZVILLE DR

HWY 164

Dever-Conner Road

NIXON DRIVE

10 S 01 E 23.00:

OR 99E (Hwy 58)

OR 99E (Hwy 58)

OR 99E (HWY 58)

Tangent Road

Ridge Drive

Lake Creek Drive

Bond Butte Road

Linn-West Road

CROOK DRIVE

ROAD

N LAKE CREEK DR

DIAMOND HILL DRIVE

OR 34 (Hwy 210)

OR 226 (HWY 211)

Diamond Hill Drive

RIVER DR

OLD BRIDGE DR

ROAD

ROAD

PLAGMANN DRIVE

10TH AVE

OR 99E (Hwy 58)

US 20 (Hwy 16)

US 20 (Hwy 16)

US 20 (Hwy 16)

I-5 (HWY 1) NB

I-5 (HWY 1) SB

7TH AVE

HWY 164

US 20 (Hwy 16)

HESS RD

ASH ST

SCRAVEL HILL ROAD

HIGH DECK ROAD

SHADY OAK LANE

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