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County · code 06105

Trinity CountyCalifornia

Trinity County is a county in California with its seat in Weaverville, formed on February 18, 1850.

  • Founded1850
  • County seatWeaverville
  • Named forTrinity River
  • Land area3,179 sq mi + 28 sq mi water
  • Population16,112 2020 Census
  • Parcels mapped16,620 checked 15 October 2026
Open the free map Click any parcel in Trinity County: acreage, parcel id, address and who publishes the map. No sign-in.

Updated

HumboldtTehamaShastaSiskiyouMendocino Weaverville Census outline · seat marked

Where it is

Trinity on the map of California

California has 58 counties and county equivalents, each with its own records office. Shapes with a page are links.

Alameda CountyAlpine CountyAmador CountyButte CountyCalaveras CountyColusa CountyContra Costa CountyDel Norte CountyEl Dorado CountyFresno CountyGlenn CountyHumboldt CountyImperial CountyInyo CountyKern CountyKings CountyLake CountyLassen CountyLos Angeles CountyMadera CountyMarin CountyMariposa CountyMendocino CountyMerced CountyModoc CountyMono CountyMonterey CountyNapa CountyNevada CountyOrange CountyPlacer CountyPlumas CountyRiverside CountySacramento CountySan Benito CountySan Bernardino CountySan Diego CountySan Francisco CountySan Joaquin CountySan Luis Obispo CountySan Mateo CountySanta Barbara CountySanta Clara CountySanta Cruz CountyShasta CountySierra CountySiskiyou CountySolano CountySonoma CountyStanislaus CountySutter CountyTehama CountyTulare CountyTuolumne CountyVentura CountyYolo CountyYuba CountyTrinity County Trinity
Counties of California · Trinity highlighted

History

Formed in 1850 from Shasta County

An old deed may name a county that no longer exists, or a boundary that has since moved.

Trinity County was created from Shasta County but was not fully organized at first, remaining attached to Shasta for judicial purposes until June 9, 1851. The county was named after the Trinity River. Trinity's boundaries changed multiple times in the 1850s with the creation of Klamath and Humboldt counties, and through territorial exchanges with Klamath, Humboldt, and Mendocino counties, including a boundary dispute with Mendocino that was resolved by the California Supreme Court in 1907.

Boundary changes from the Newberry Library, Atlas of Historical County Boundaries; the 5 that matter most are shown first.

  1. 1850
    Trinity County created Trinity created from non-county area; Trinity not fully organized, attached to Shasta for judicial and other purposes.
    from Shasta
    · Calif. Stats. 1849, 1st sess., ch. 15, sec. 24/p. 62
  2. 1851
    Lost territory Trinity lost to creation of Klamath (extinct).
    to Klamath
    · Calif. Stats. 1851, 2d sess., ch. 14, secs. 30-31/pp. 179-180
  3. 1853
    Lost territory Trinity lost to creation of Humboldt.
    to Humboldt
    · Calif. Stats. 1853, 4th sess., ch. 114/pp. 161-164
  4. 1855
    Gained territory Trinity gained from Klamath (extinct).
    from Klamath
    · Calif. Stats. 1855, 6th sess., ch. 156/p. 200
  5. 1859
    Lost territory Trinity lost to Mendocino.
    to Mendocino
    · Calif. Stats. 1859, 10th sess., ch. 108/pp. 98-99
Show all 8 changes (3 more)
  1. 1850
    Trinity County created Trinity created from non-county area; Trinity not fully organized, attached to Shasta for judicial and other purposes.
    from Shasta
    · Calif. Stats. 1849, 1st sess., ch. 15, sec. 24/p. 62
  2. 1851
    Lost territory Trinity lost to creation of Klamath (extinct).
    to Klamath
    · Calif. Stats. 1851, 2d sess., ch. 14, secs. 30-31/pp. 179-180
  3. 1851
    Changed Trinity fully organized; detached from Shasta.
    Shasta
    · Calif. Stats. 1851, 2d sess., ch. 132/pp. 516-518; Cox, 116-117
  4. 1853
    Lost territory Trinity lost to creation of Humboldt.
    to Humboldt
    · Calif. Stats. 1853, 4th sess., ch. 114/pp. 161-164
  5. 1855
    Gained territory Trinity gained from Klamath (extinct).
    from Klamath
    · Calif. Stats. 1855, 6th sess., ch. 156/p. 200
  6. 1859
    Lost territory Trinity lost to Mendocino.
    to Mendocino
    · Calif. Stats. 1859, 10th sess., ch. 108/pp. 98-99
  7. 1860
    Gained territory Trinity gained from Mendocino.
    from Mendocino
    · Calif. Stats. 1860, 11th sess., ch. 340/p. 334
  8. 1872
    Gained territory Trinity gained from Mendocino when their common boundary was surveyed; later Mendocino claimed a different boundary based on an 1891 survey. California Supreme Court upheld 1872 survey on 15 May 1907.
    from Mendocino
    · Calif. Stats. 1871, 19th sess., ch. 531/p. 766; "Trinity County v. Mendocino County," in Calif. Rpts., 151: 279-289

Land and parcels

What the maps cover in Trinity

Who publishes each layer, how good it is, and when we last checked.

Official
from the office that keeps the record
Good enough
a reliable statewide or national copy
Fallback
a guide only; check the official record
Missing
nothing public found yet

People and land

Trinity by the Census

Population
16,112 2020 Census count
Housing units
8,183 2020 Census count
Land area
3,179 square miles
Water area
28 square miles
People per sq mi
5 population ÷ land area

Source: US Census Bureau, 2020 Census; US Census Bureau, 2020 Gazetteer Files. Not endorsed or certified by the Census Bureau.

Rules and offices

Who to ask before you build, dig or sell

Official county pages only. We link to them; we do not copy them, because they change.

Inside a city or town, permits usually come from that city rather than the county.

Records

Permits

Zoning and code

County government

See your own lot on these maps

Open Trinity County on Parcel Chart's free map and click your parcel. Save it with a free account; the full record of your place (site map, projects, documents) is Pro, in early access.

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Questions

Common questions about Trinity County

When was Trinity County founded?
Trinity County was founded in 1850, formed from Shasta County, and named after Trinity River.
What is the county seat of Trinity County?
The county seat of Trinity County is Weaverville.
Is there an online parcel map for Trinity County?
Yes. Trinity County publishes a parcel map of 16,620 parcels, rated good enough here. You can click any parcel on it in Parcel Chart's free map, no sign-in needed.
Has Trinity County's boundary or name changed?
Trinity County was created in 1850 from Shasta County. Since then the Atlas of Historical County Boundaries records 7 later changes, chiefly involving Mendocino County, Klamath County and Humboldt County.
Who issues building permits in Trinity County?
The county's page on building permits: Building Permit. Inside a city or town, ask that city first.
Who issues septic and well permits in Trinity County?
The county's page on septic systems and wells: Behavioral Health.
Is my lot in a flood zone?
We do not have flood maps for Trinity County yet. Look up the address on FEMA's Flood Map Service Center, which shows the effective flood map for any lot.

Nearby

Counties next door