Total bridges
421
Public highway bridges in Siskiyou County
County profile · official public datasets
Siskiyou County, CA
421 public highway bridges tracked in the FHWA National Bridge Inventory: 39% rated Good, 55.6% Fair, 5.5% Poor.
- 421
- Public bridges
- 39%
- Good condition
- 5.5%
- Poor condition
The verdict
According to the Federal Highway Administration's 2024 National Bridge Inventory.
Siskiyou County posts a better-than-median Poor-condition share among rated counties in the state across mid-size county bridge inventory.
- Top 29%
- lowest Poor share in state
- 5.5%
- Poor-condition share
- 421
- 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.
Siskiyou County Bridge Snapshot
According to the Federal Highway Administration's 2024 National Bridge Inventory, Siskiyou County ranks #17 of 58 California counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 5.5%). Siskiyou County, California contains 421 public highway bridges. Roughly 39% are rated “Good,” 55.6% “Fair,” and 5.5% “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
39%
164 of 421 rated 7-9
Fair condition
55.6%
234 of 421 rated 5-6
Poor condition
5.5%
23 of 421 rated 4 or below
In-state Poor-share rank
#17 of 58
Among California counties with 5+ bridges, lower share ranks better
Condition distribution
Share of 421 NBI-tracked bridges by lowest applicable component rating.
Good 39% (164)
Fair 55.6% (234)
Poor 5.5% (23)
Siskiyou County's Poor-condition bridges carry 3,115 vehicle crossings a day
That is 0.4% of the county's reported daily bridge traffic on 5.5% of its bridges: Poor-condition structures carry less traffic than their share of the inventory. Each Poor bridge averages 135 crossings a day against 1,929 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 420 of 421 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.
67.9% of Siskiyou County's bridges have passed the 50-year mark
286 of the 421 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 39% 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 19.7% of the county's Poor-condition bridge traffic
STATE ROUTE 96 over THOMPSON CREEK, built 1952, carries 615 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 23-bridge count understates how much of the daily burden sits on a single crossing.
Share is of the 3,115 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.
When Siskiyou County's bridges were built
421 bridges with a recorded construction year, grouped by decade
- 1900s 2
1900–1909
2 bridges
- 1910s 5
1910–1919
5 bridges
- 1920s 8
1920–1929
8 bridges
- 1930s 10
1930–1939
10 bridges
- 1940s 9
1940–1949
9 bridges
- 1950s 47
1950–1959
47 bridges
- 1960s
1960–1969
134 bridges
- 1970s
1970–1979
106 bridges
- 1980s 42
1980–1989
42 bridges
- 1990s 20
1990–1999
20 bridges
- 2000s 29
2000–2009
29 bridges
- 2010s 6
2010–2019
6 bridges
- 2020s 3
2020–2029
3 bridges
What this shows Construction peaked in the 1960s, when 134 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 California average (1970).
How Siskiyou County compares with California's closest counties by inventory size
The 5 California counties nearest Siskiyou County in number of bridges, with their condition splits. Its 5.5% Poor share is the 1st-lowest of these 6. Its average build year of 1971 against a peer-group mean of 1968 is in line with the group.
Showing the 5 closest of 57 California counties eligible for comparison.
| County | Bridges | Good | Fair | Poor | Avg. built |
|---|---|---|---|---|---|
| Imperial County | 444 | 50.7% | 40.5% | 8.8% | 1968 |
| Butte County | 437 | 31.8% | 62% | 6.2% | 1958 |
| Siskiyou County (this page) | 421 | 39% | 55.6% | 5.5% | 1971 |
| 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 | 396 | 38.9% | 54.3% | 6.8% | 1968 |
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 Siskiyou 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 Siskiyou County, both outside California so the neighborhoods are not the same-state size table above.
Similar inventory size
Nearest county inventories outside CA (421 bridges here).
- Fayette County, PA · 422 bridges
- Kay County, OK · 419 bridges
- Taylor County, TX · 419 bridges
- Lewis County, WA · 419 bridges
Similar average build year
Nearest mean year-built outside CA (1971 here).
- Wayne County, MI · avg 1971 · 1,026 bridges
- Baltimore County, MD · avg 1971 · 783 bridges
- Washington County, PA · avg 1971 · 655 bridges
- Linn County, OR · avg 1971 · 566 bridges
Source: FHWA National Bridge Inventory, 2024 release. Peers floor at 10 bridges so stub inventories cannot own the match.
Fair-condition bridges (234)
STATE ROUTE 3
FairOver: SOUTH FORK SCOTT RIVER
02-SIS-003-8.89, Siskiyou, CA
Built 1958 Load: 46.0 t ADT: 345
GAZELLE-CALLAHAN R
FairOver: NOYES VALLEY CREEK
0.1 MI N MASTERSON RD, Siskiyou, CA
Built 1972 Load: 46.0 t ADT: 287
FRENCH CREEK RD
FairOver: FRENCH CREEK
5.2 MI S OF S.H. 3, Siskiyou, CA
Built 1990 Load: 46.3 t ADT: 20
CECILVILLE ROAD
FairOver: MCNEAL CREEK
1 MI S/O SALMON RIVER RD, Siskiyou, CA
Built 1937 Load: 46.7 t ADT: 101
INTERSTATE 5 SB
FairOver: SISKIYOU WAY
02-SIS-005-R18.71-WEED, Siskiyou, CA
Built 1973 Load: 47.3 t ADT: 7,150
CARIBOU ROAD
FairOver: RAYS GULCH
4.7 MI S/O CECILVILLE RD, Siskiyou, CA
Built 1982 Load: 47.3 t ADT: 29
INTERSTATE 5 NB
FairOver: HUTTON CREEK
02-SIS-005-R64.82R, Siskiyou, CA
Built 1974 Load: 47.6 t ADT: 15,300
INTERSTATE 5 NB
FairOver: HENLEY WAY
02-SIS-005-R61.55, Siskiyou, CA
Built 1974 Load: 48.0 t ADT: 7,650
INTERSTATE 5 NB
FairOver: COTTONWOOD CREEK
02-SIS-005-R63.65R, Siskiyou, CA
Built 1974 Load: 48.3 t ADT: 15,300
SLOUGH ROAD
FairOver: INTERSTATE 5
02-SIS-005-R34.96, Siskiyou, CA
Built 1969 Load: 48.6 t ADT: 10
DOOLITTLE CREEK RD
FairOver: INDIAN CREEK
AT INDIAN CREEK RD, Siskiyou, CA
Built 1965 Load: 48.6 t ADT: 79
LOUIE ROAD
FairOver: INTERSTATE 5
02-SIS-005-R31.18, Siskiyou, CA
Built 1969 Load: 51.5 t ADT: 40
MCADAMS CREEK RD
FairOver: MOFFETT CREEK
0.25 MI N SR 3, Siskiyou, CA
Built 1978 Load: 52.8 t ADT: 256
CECILVILLE ROAD
FairOver: NORTH FORK SALMON RIVER
S/O SALMON RIVER ROAD, Siskiyou, CA
Built 1985 Load: 54.4 t ADT: 116
EAST-WEST RD
FairOver: LOST RIVER
1.8 MI W SR 139, Siskiyou, CA
Built 1984 Load: 54.4 t ADT: 827
GRIDER ROAD
FairOver: GRIDER CREEK
2.7 MI S SR 96, Siskiyou, CA
Built 1976 Load: 54.4 t ADT: 94
FRENCH CR RD
FairOver: FRENCH CREEK
3.7 MI S SR 3, Siskiyou, CA
Built 1986 Load: 54.4 t ADT: 245
INTERSTATE 5 SB
FairOver: COTTONWOOD CREEK
02-SIS-005-R63.77L, Siskiyou, CA
Built 1974 Load: 55.1 t ADT: 7,300
CURLY JACK ROAD
FairOver: ELK CREEK
0.8 MI S OF ELK CREEK RD, Siskiyou, CA
Built 1975 Load: 55.4 t ADT: 624
INTERSTATE 5 SB
FairOver: HENLEY WAY
02-SIS-005-R61.55, Siskiyou, CA
Built 1974 Load: 56.7 t ADT: 7,650
ANDERSON GRADE RD
FairOver: YREKA CREEK
0.1 MI E OF SR 263, Siskiyou, CA
Built 1971 Load: 56.7 t ADT: 90
ISLAND ROAD
FairOver: SCOTT RIVER OVERFLOW
0.5 MI E HOLZHAUSER LANE, Siskiyou, CA
Built 1977 Load: 57.0 t ADT: 158
ISLAND ROAD
FairOver: SCOTT RIVER OVERFLOW
0.2 MI W OF EASTSIDE RD, Siskiyou, CA
Built 1977 Load: 57.3 t ADT: 161
ISLAND ROAD
FairOver: SCOTT RIVER OVERFLOW
0.1 MI W OF ISLAND RD, Siskiyou, CA
Built 1977 Load: 58.3 t ADT: 86
EDGEWOOD ROAD
FairOver: SHASTA RIVER
0.1 MI W OL EDGEWOOD WEED, Siskiyou, CA
Built 1973 Load: 59.9 t ADT: 395
CARIBOU ROAD
FairOver: SOUTH FORK SALMON RIVER
4 MI S/O CECILVILLE ROAD, Siskiyou, CA
Built 1984 Load: 64.8 t ADT: 48
TENNANT RD
FairOver: ANTELOPE CREEK
11.6 MI SE SR97, Siskiyou, CA
Built 1971 Load: 66.4 t ADT: 79
SAWYERS BAR RD
FairOver: NORTH FORK SALMON RIVER
3 MI N WHITES GULCH RD, Siskiyou, CA
Built 1982 Load: 68.0 t ADT: 105
MCADAMS CREEK RD
FairOver: MCADAMS CREEK
2.55 MI N SR 3, Siskiyou, CA
Built 1975 Load: 73.9 t ADT: 256
SLOUGH RD
FairOver: LOWER PARKS CREEK
4.1 MI S OF LOUIE RD, Siskiyou, CA
Built 1975 Load: 76.8 t ADT: 7
CECILVILLE ROAD
FairOver: SOUTH FORK SALMON RIVER
0.1 MI S/O SALMON RIVER R, Siskiyou, CA
Built 1986 Load: 78.1 t ADT: 116
FISH LAKE ROAD
FairOver: E. FORK SALMON RIVER
CALLAHAN, Siskiyou, CA
Built 1966 Load: 90.8 t ADT: 15
WRIGHTS LAKE ROAD
FairOver: BOULDER CREEK
SCOTT BAR, Siskiyou, CA
Built 1967 Load: 90.8 t ADT: 50
INTERSTATE 5
FairOver: LITTLE CASTLE CREEK
02-SIS-005-0.04, Siskiyou, CA
Built 1960 Load: 99.9 t ADT: 18,000
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.