County profile · official public datasets

Modoc County, CA

87 public highway bridges tracked in the FHWA National Bridge Inventory: 49.4% rated Good, 49.4% Fair, 1.1% Poor.

87
Public bridges: 49.4%
Good condition: 1.1%
Poor condition

The verdict

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

Modoc County posts a top-5% lowest Poor-condition share among rated counties in the state across rated county bridge inventory.

Top 2%
lowest Poor share in state: 1.1%
Poor-condition share: 87
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.

Modoc County Bridge Snapshot

According to the Federal Highway Administration's 2024 National Bridge Inventory, Modoc County ranks #1 of 58 California counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 1.1%). Modoc County, California contains 87 public highway bridges. Roughly 49.4% are rated “Good,” 49.4% “Fair,” and 1.1% “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

Public highway bridges in Modoc County

Good condition

49.4%

43 of 87 rated 7-9

Fair condition

49.4%

43 of 87 rated 5-6

Poor condition

1.1%

1 of 87 rated 4 or below

In-state Poor-share rank

#1 of 58

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

Condition distribution

Share of 87 NBI-tracked bridges by lowest applicable component rating.

Good

49.4% (43)

Fair

49.4% (43)

Poor

1.1% (1)

Modoc County's Poor-condition bridges carry 1,200 vehicle crossings a day

That is 1.9% of the county's reported daily bridge traffic on 1.2% of its bridges: Poor-condition structures carry more traffic than their share of the inventory. Each Poor bridge averages 1,200 crossings a day against 594 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 86 of 87 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.

66.7% of Modoc County's bridges have passed the 50-year mark

58 of the 87 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 49.4% 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 100% of the county's Poor-condition bridge traffic

STATE ROUTE 299 over PIT RIVER, built 1962, carries 1,200 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 1-bridge count understates how much of the daily burden sits on a single crossing.

Share is of the 1,200 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.

1910s

1
1920s

3
1930s

6
1940s

3
1950s

25
1960s

9
1970s

15
1980s

5
1990s

6
2000s

6
2010s

6
2020s

2

What this shows Construction peaked in the 1950s, when 25 of the county's bridges still in the inventory were built, which is 28.7% of those with a recorded year. That cohort is now 65 to 74 years old in the 2024 inventory. Its average build year (1969) matches the California average (1970).

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

The 5 California counties nearest Modoc County in number of bridges, with their condition splits. Its 1.1% Poor share is the 1st-lowest of these 6. Its average build year of 1969 against a peer-group mean of 1970 is in line with the group.

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

Bridge inventory size and condition shares for Modoc County and the 5 California counties closest to it in inventory size
County	Bridges	Good	Fair	Poor	Avg. built
Lassen County	108	25.9%	65.7%	8.3%	1968
Calaveras County	105	33.3%	60%	6.7%	1962
Del Norte County	96	51%	37.5%	11.5%	1975
Modoc County (this page)	87	49.4%	49.4%	1.1%	1969
San Benito County	76	46.1%	43.4%	10.5%	1971
Inyo County	66	63.6%	31.8%	4.5%	1972

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

Similar inventory size

Nearest county inventories outside CA (87 bridges here).

Hendry County, FL · 87 bridges
Adams County, ID · 87 bridges
Humboldt County, IA · 87 bridges
Rockcastle County, KY · 87 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 87 Good 43 Fair 43 Poor 1

All bridges (87)

Sort:

Modoc County Bridge Snapshot

Condition distribution

Modoc County's Poor-condition bridges carry 1,200 vehicle crossings a day

66.7% of Modoc County's bridges have passed the 50-year mark

One structure carries 100% of the county's Poor-condition bridge traffic

How Modoc 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

All bridges (87)

42N31

42N35

CR 87A

41N11

STATE ROUTE 299

COUNTY ROAD 215

SURPRISE VALLEY RD

MAINE ST

CO RD 198

COUNTY ROAD 75

U.S. HIGHWAY 395

STATE ROUTE 299

STATE ROUTE 299

ESTES STREET

CO RD 56

NO DATA ENTERED

BLUE LAKE ROAD

CENTERVILLE RD

ROAD 63

OLD BLUE LAKE ROAD

CR 64/JESS VALLEY

LOOKOUT-HACKMORE R

U.S. HIGHWAY 395

CR 54/CENTERVILLE

IRR ALPINE RD. 58

CENTERVILLE RD

IRR CO RD 87

CR 71

CO RD 133C

CO RD 60

CR 85

JONES LN -CO RD 61

STATE ROUTE 139

IRR BIA RTE 76

COUNTY ROAD 60

STATE ROUTE 139

U.S. HIGHWAY 395

U.S. HIGHWAY 395

IRR CO RD 87

U.S. HIGHWAY 395

U.S. HIGHWAY 395

U.S. HIGHWAY 395

COUNTY ROAD 112

42N16

FOREST ROAD 22

48N48

38N54

COUNTY ROAD 215

SOUTH WARNER ROAD

COUNTY ROAD 70

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