Total bridges
396
Public highway bridges in Humboldt County
County profile · official public datasets
Humboldt County, CA
396 public highway bridges tracked in the FHWA National Bridge Inventory: 38.9% rated Good, 54.3% Fair, 6.8% Poor.
- 396
- Public bridges
- 38.9%
- Good condition
- 6.8%
- Poor condition
The verdict
According to the Federal Highway Administration's 2024 National Bridge Inventory.
Humboldt County posts a better-than-median Poor-condition share among rated counties in the state across mid-size county bridge inventory.
- Top 50%
- lowest Poor share in state
- 6.8%
- Poor-condition share
- 396
- public highway bridges
- 1968
- 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.
Humboldt County Bridge Snapshot
According to the Federal Highway Administration's 2024 National Bridge Inventory, Humboldt County ranks #29 of 58 California counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 6.8%). Humboldt County, California contains 396 public highway bridges. Roughly 38.9% are rated “Good,” 54.3% “Fair,” and 6.8% “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.
Good condition
38.9%
154 of 396 rated 7-9
Fair condition
54.3%
215 of 396 rated 5-6
Poor condition
6.8%
27 of 396 rated 4 or below
In-state Poor-share rank
#29 of 58
Among California counties with 5+ bridges, lower share ranks better
Condition distribution
Share of 396 NBI-tracked bridges by lowest applicable component rating.
Good 38.9% (154)
Fair 54.3% (215)
Poor 6.8% (27)
Humboldt County's Poor-condition bridges carry 42,605 vehicle crossings a day
That is 3% of the county's reported daily bridge traffic on 6.8% of its bridges: Poor-condition structures carry less traffic than their share of the inventory. Each Poor bridge averages 1,578 crossings a day against 4,152 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 396 of 396 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.
69.2% of Humboldt County's bridges have passed the 50-year mark
274 of the 396 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 38.9% 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 41.1% of the county's Poor-condition bridge traffic
US HIGHWAY 101 NB over WEST END RD CREEK NCRRA, built 1929, carries 17,500 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 42,605 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.
When Humboldt County's bridges were built
396 bridges with a recorded construction year, grouped by decade
- 1910s 3
1910–1919
3 bridges
- 1920s 16
1920–1929
16 bridges
- 1930s 17
1930–1939
17 bridges
- 1940s 13
1940–1949
13 bridges
- 1950s
1950–1959
63 bridges
- 1960s
1960–1969
135 bridges
- 1970s 52
1970–1979
52 bridges
- 1980s 46
1980–1989
46 bridges
- 1990s 25
1990–1999
25 bridges
- 2000s 9
2000–2009
9 bridges
- 2010s 13
2010–2019
13 bridges
- 2020s 4
2020–2029
4 bridges
What this shows Construction peaked in the 1960s, when 135 of the county's bridges still in the inventory were built, which is 34.1% of those with a recorded year. That cohort is now 55 to 64 years old in the 2024 inventory. Its average build year (1968) matches the California average (1970).
How Humboldt County compares with California's closest counties by inventory size
The 5 California counties nearest Humboldt County in number of bridges, with their condition splits. Its 6.8% Poor share is the 3rd-lowest of these 6. Its average build year of 1968 against a peer-group mean of 1969 is in line with the group.
Showing the 5 closest of 57 California counties eligible for comparison.
| County | Bridges | Good | Fair | Poor | Avg. built |
|---|---|---|---|---|---|
| Santa Barbara County | 418 | 51.4% | 42.8% | 5.7% | 1975 |
| San Luis Obispo County | 401 | 47.6% | 46.6% | 5.7% | 1970 |
| Humboldt County (this page) | 396 | 38.9% | 54.3% | 6.8% | 1968 |
| 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 |
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 Humboldt 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 Humboldt County, both outside California so the neighborhoods are not the same-state size table above.
Similar inventory size
Nearest county inventories outside CA (396 bridges here).
- Nodaway County, MO · 396 bridges
- Somerset County, NJ · 397 bridges
- Essex County, MA · 395 bridges
- Creek County, OK · 395 bridges
Similar average build year
Nearest mean year-built outside CA (1968 here).
- Montgomery County, PA · avg 1968 · 828 bridges
- Providence County, RI · avg 1968 · 476 bridges
- Delaware County, PA · avg 1968 · 387 bridges
- Genesee County, MI · avg 1968 · 371 bridges
Source: FHWA National Bridge Inventory, 2024 release. Peers floor at 10 bridges so stub inventories cannot own the match.
All bridges (396)
CHEZEM RD
FairOver: REDWOOD CREEK
1.5 MI E HIGHWAY 299, Humboldt, CA
Built 1916 Load: 5.8 t ADT: 78
STATE ROUTE 96
FairOver: SLATE CREEK
01-HUM-096-29.92, Humboldt, CA
Built 1960 Load: 12.3 t ADT: 540
U.S. HIGHWAY 101
FairOver: JONES SLOUGH
01-HUM-101-88.87, Humboldt, CA
Built 1959 Load: 14.3 t ADT: 12,900
BRICELAND-THORNE
FairOver: REDWOOD CREEK
3.3 MI W JCT US 101, Humboldt, CA
Built 1938 Load: 14.3 t ADT: 1,836
ALDERPOINT ROAD
FairOver: COOPER CREEK
30.4 MI E/N S.H. 101, Humboldt, CA
Built 1952 Load: 14.3 t ADT: 250
ELK RIVER ROAD
FairOver: NORTH FORK ELK RIVER
NE PEPPER ST, Humboldt, CA
Built 1923 Load: 14.6 t ADT: 156
PRICE CREEK ROAD
FairOver: PRICE CREEK
0.2 MI W/O BLUE SLIDE RD, Humboldt, CA
Built 1940 Load: 14.6 t ADT: 118
ARLINGTON AVENUE
FairOver: FRANCIS CREEK
JUST W SR 211 IN FERNDALE, Humboldt, CA
Built 2001 Load: 15.2 t ADT: 500
COFFEE CREEK ROAD
FairOver: PERRY SLOUGH
0.2 MI SOUTH OF RTE 211, Humboldt, CA
Built 1931 Load: 15.6 t ADT: 254
STATE ROUTE 36
FairOver: YAGER CREEK
01-HUM-036-4.86, Humboldt, CA
Built 1968 Load: 15.9 t ADT: 2,800
BRICELAND RD
FairOver: REDWOOD CREEK
10 MI E SHELTER COVE RD, Humboldt, CA
Built 1935 Load: 16.2 t ADT: 1,836
MAPLE CREEK ROAD
FairOver: BOULDER CREEK
1/4 MI E BUTLER VLY RD, Humboldt, CA
Built 1923 Load: 16.2 t ADT: 106
ALDERPOINT RD
FairOver: MARTIN CREEK
6.7 MI SOUTH BRIDGEVILLE, Humboldt, CA
Built 1972 Load: 16.2 t ADT: 124
JACK SHAW ROAD
FairOver: BILLINGS CREEK
1.3 MI E MOUNTAIN VIEW, Humboldt, CA
Built 1987 Load: 16.2 t ADT: 50
12TH ST
FairOver: ROHNER CREEK
0.1 MILE NORTH NEWBURG RD, Humboldt, CA
Built 1935 Load: 16.2 t ADT: 3,160
MAIN STREET
FairOver: ROHNER CREEK
JUST EAST OF 16TH STREET, Humboldt, CA
Built 1922 Load: 16.5 t ADT: 11,181
HOLMES FLAT RD
FairOver: EEL RIVER
NEAR HOLMES, Humboldt, CA
Built 1999 Load: 16.7 t ADT: 100
ETSBRG HNYDEW RD
FairOver: MATTOLE RIVER
5.77 MI N/O THORNE RD, Humboldt, CA
Built 1928 Load: 16.8 t ADT: 200
HOWE CREEK ROAD
FairOver: HOWE CREEK
2.1 MI S/O BLUE SLIDE RD, Humboldt, CA
Built 2006 Load: 16.8 t ADT: 19
FULMOR ROAD
FairOver: SALT RIVER
NORTH OF KENYON ROAD, Humboldt, CA
Built 1950 Load: 17.2 t ADT: 246
REDWOOD DR
FairOver: DEAN CREEK
N/O REDWAY ADJ TO US 101, Humboldt, CA
Built 1933 Load: 17.2 t ADT: 1,978
SHOWER PASS RD
FairOver: OLSEN CREEK
6.1 MI NE/O KNEELAND RD, Humboldt, CA
Built 1966 Load: 17.2 t ADT: 7
STATE ROUTE 96
FairOver: HILLSIDE
01-HUM-096-8.26, Humboldt, CA
Built 1985 Load: 17.5 t ADT: 2,900
ZANES RD
FairOver: ELK RIVER
0.1 MI W ELK RIVER RD, Humboldt, CA
Built 1936 Load: 17.5 t ADT: 38
OLD MATTOLE RD
FairOver: MCNUTT CREEK
0.49 MI N OF MATTOLE RD, Humboldt, CA
Built 1926 Load: 17.5 t ADT: 100
BERTA RD
FairOver: ELK RIVER
0.14 MI W ELK RIVER RD, Humboldt, CA
Built 1936 Load: 17.8 t ADT: 518
ALBERT ETTER RA RD
FairOver: BEAR CREEK
0.2 MI SW/O ETRSBG-HNYDW, Humboldt, CA
Built 1985 Load: 17.8 t ADT: 50
BAIR ROAD
FairOver: REDWOOD CREEK
3.4 MI N/O SR 299, Humboldt, CA
Built 1950 Load: 18.1 t ADT: 113
BRICELAND ROAD
FairOver: REDWOOD CREEK
0.1 MI E BRICELND THO RD, Humboldt, CA
Built 1949 Load: 18.1 t ADT: 250
WHITLOW ROAD
FairOver: SONOMA CREEK #2
2.4 MI E OF ELK CREEK RD, Humboldt, CA
Built 1966 Load: 18.8 t ADT: 53
WHITLOW ROAD
FairOver: SONOMA CREEK #1
2.2 MI E OF ELK CREEK RD, Humboldt, CA
Built 1966 Load: 18.8 t ADT: 53
FOREST ROAD
FairOver: SOUTH FORK EEL RIVER
0.1 MI W/O REDWOOD DR, Humboldt, CA
Built 1965 Load: 18.8 t ADT: 110
ELINOR ROAD
FairOver: GREENLOW CREEK
0.3 MILE NE OF ROUTE 254, Humboldt, CA
Built 1988 Load: 19.1 t ADT: 20
MATTOLE RD
FairOver: DRY CREEK
1 MI S/O SINGLEY CREEK, Humboldt, CA
Built 1985 Load: 19.4 t ADT: 196
ALDERPOINT RD
FairOver: CONLEY CREEK
1 MI S OF BLOCKSBURG, Humboldt, CA
Built 1990 Load: 20.1 t ADT: 114
BRICELAND-THORNE
FairOver: MCKEE CREEK
0.1 MI S/O SHELTER COVE, Humboldt, CA
Built 1952 Load: 20.1 t ADT: 420
STATE ROUTE 283
FairOver: EEL RIVER & NWP RR
01-HUM-283-0.12, Humboldt, CA
Built 1941 Load: 20.4 t ADT: 2,150
HOWARD HEIGHTS RD
FairOver: FRESHWATER CREEK
0.01 MI SW FRESHWATER RD, Humboldt, CA
Built 1949 Load: 20.4 t ADT: 172
BROOKWOOD DRIVE
FairOver: JACOBY CREEK
0.1 MI S/O JACOBY CRK RD, Humboldt, CA
Built 1967 Load: 20.4 t ADT: 162
STATE ROUTE 299
FairOver: EAST FORK WILLOW CREEK
01-HUM-299-33.21, Humboldt, CA
Built 1956 Load: 20.7 t ADT: 3,200
STATE ROUTE 255
FairOver: SAMOA CHANNEL
01-HUM-255-1.37-EUR, Humboldt, CA
Built 1971 Load: 20.7 t ADT: 7,300
BRICELAND ROAD
FairOver: REDWOOD CREEK (REDWAY)
WHITTEMORE STATE PARK, Humboldt, CA
Built 1938 Load: 20.7 t ADT: 260
COUNTRY CLUB RD
FairOver: TRINITY RIVER
IN WILLOW CREEK, Humboldt, CA
Built 1957 Load: 21.1 t ADT: 2,947
MATTOLE ROAD
FairOver: NORTH FORK MATTOLE RIVER
1.3 NW OF MATTOLE RIVER, Humboldt, CA
Built 1961 Load: 21.1 t ADT: 219
BRICELAND-THORNE
FairOver: SOUTH FORK EEL RIVER
1.1 MI W JCT OLD RTE 101, Humboldt, CA
Built 1966 Load: 21.4 t ADT: 2,468
STATE ROUTE 299
FairOver: WILLOW CREEK
01-HUM-299-34.56, Humboldt, CA
Built 1955 Load: 21.7 t ADT: 3,200
ISHI PISHI RD
FairOver: KLAMATH RIVER
0.5 MI SW OF SR 96, Humboldt, CA
Built 1967 Load: 21.7 t ADT: 71
BUTLER VALLEY RD
FairOver: MAD RIVER
0.1 MI E/O BLACK CRK LN, Humboldt, CA
Built 1937 Load: 22.0 t ADT: 105
WEST END ROAD
FairOver: WARREN CREEK
0.2 MI S WARREN CREEK RD, Humboldt, CA
Built 1927 Load: 22.0 t ADT: 472
ROHNERVILLE ROAD
FairOver: STRONGS CREEK
0.3 MI W OF NEWBURG RD, Humboldt, CA
Built 1915 Load: 22.4 t ADT: 4,924
Read our methodology - how this data is sourced, computed, and verified.
Related
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.