County profile · official public datasets

Mendocino County, CA

357 public highway bridges tracked in the FHWA National Bridge Inventory: 34.7% rated Good, 57.7% Fair, 7.6% Poor.

357
Public bridges: 34.7%
Good condition: 7.6%
Poor condition

The verdict

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

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

34th
of 58 on Poor share: 7.6%
Poor-condition share: 357
public highway bridges: 1969
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.

Mendocino County Bridge Snapshot

According to the Federal Highway Administration's 2024 National Bridge Inventory, Mendocino County ranks #34 of 58 California counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 7.6%). Mendocino County, California contains 357 public highway bridges. Roughly 34.7% are rated “Good,” 57.7% “Fair,” and 7.6% “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

357

Public highway bridges in Mendocino County

Good condition

34.7%

124 of 357 rated 7-9

Fair condition

57.7%

206 of 357 rated 5-6

Poor condition

7.6%

27 of 357 rated 4 or below

In-state Poor-share rank

#34 of 58

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

Condition distribution

Share of 357 NBI-tracked bridges by lowest applicable component rating.

Good

34.7% (124)

Fair

57.7% (206)

Poor

7.6% (27)

Mendocino County's Poor-condition bridges carry 54,128 vehicle crossings a day

That is 3.6% of the county's reported daily bridge traffic on 7.6% of its bridges: Poor-condition structures carry less traffic than their share of the inventory. Each Poor bridge averages 2,005 crossings a day against 5,465 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 357 of 357 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.

64.7% of Mendocino County's bridges have passed the 50-year mark

231 of the 357 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 34.7% 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 21.2% of the county's Poor-condition bridge traffic

STATE ROUTE 20 over RUSSIAN RIV NCRA/NWP RR, built 1958, carries 11,500 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 27-bridge count understates how much of the daily burden sits on a single crossing.

Share is of the 54,128 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.

pre-1900

1
1910s

3
1920s

8
1930s

25
1940s

27
1950s

58
1960s

93
1970s

29
1980s

43
1990s

27
2000s

13
2010s

28
2020s

2

What this shows Construction peaked in the 1960s, when 93 of the county's bridges still in the inventory were built, which is 26.1% of those with a recorded year. That cohort is now 55 to 64 years old in the 2024 inventory. Its average build year (1969) matches the California average (1970).

How Mendocino County compares with California's closest counties by inventory size

The 5 California counties nearest Mendocino County in number of bridges, with their condition splits. Its 7.6% Poor share is the 2nd-lowest of these 6. Its average build year of 1969 against a peer-group mean of 1969 is in line with the group.

Showing the 5 closest of 57 California counties eligible for comparison.

Bridge inventory size and condition shares for Mendocino County and the 5 California counties closest to it in inventory size
County	Bridges	Good	Fair	Poor	Avg. built
Stanislaus County	386	30.8%	55.7%	13.5%	1956
Monterey County	377	56.8%	35.5%	7.7%	1970
Solano County	373	44.8%	47.5%	7.8%	1975
San Mateo County	361	26%	64%	10%	1967
Mendocino County (this page)	357	34.7%	57.7%	7.6%	1969
Placer County	337	44.2%	51.6%	4.2%	1976

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

Similar inventory size

Nearest county inventories outside CA (357 bridges here).

Fayette County, IL · 357 bridges
Hancock County, OH · 357 bridges
Preble County, OH · 357 bridges
Augusta County, VA · 357 bridges

Similar average build year

Nearest mean year-built outside CA (1969 here).

Cook County, IL · avg 1969 · 1,721 bridges
Cuyahoga County, OH · avg 1969 · 871 bridges
Somerset County, PA · avg 1969 · 454 bridges
Lewis County, WA · avg 1969 · 419 bridges

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

All 357 Good 124 Fair 206 Poor 27

Good-condition bridges (124)

Sort:

Mendocino County Bridge Snapshot

Condition distribution

Mendocino County's Poor-condition bridges carry 54,128 vehicle crossings a day

64.7% of Mendocino County's bridges have passed the 50-year mark

One structure carries 21.2% of the county's Poor-condition bridge traffic

How Mendocino County compares with California's closest counties by inventory size

Nationwide counties with similar inventory size or average build year

Similar inventory size

Similar average build year

Good-condition bridges (124)

RG STATE PARK ROAD

SOUTH MAIN STREET

U.S. HIGHWAY 101

MAIN ST

ANDERSON VALLEY HW

MOUNTAIN HOUSE RD

CENTER VALLEY RD

STATE ROUTE 1

STATE ROUTE 128

US HIGHWAY 101 SB

US HIGHWAY 101 NB

U.S. HIGHWAY 101

STEELE RD

STATE ROUTE 175

U.S. HIGHWAY 101

STATE ROUTE 1

STATE ROUTE 20

STATE ROUTE 1

STATE ROUTE 162

U.S. HIGHWAY 101

FOREST ROAD 360

FOREST ROAD 300

STATE ROUTE 128

STATE ROUTE 20

US HIGHWAY 101 SB

US HIGHWAY 101 NB

STATE ROUTE 1

BRANSCOMB RD

STATE ROUTE 1

US HIGHWAY 101 SB

US HIGHWAY 101 NB

IRR MINA RD

STATE ROUTE 162

STATE ROUTE 271

BRANSCOMB RD

RUDDCK-CUNNINHM RD

STATE ROUTE 1

ORR SPRINGS ROAD

HEARST-WILLITS RD

US HIGHWAY 101 SB

US HIGHWAY 101 NB

STATE ROUTE 128

STATE ROUTE 162

STATE ROUTE 20

STATE ROUTE 20

RTE 101S - RTE 20W

RTE 20E - RTE 101N

STATE ROUTE 1

STATE ROUTE 1

US HIGHWAY 101

Related