Trinity County is a county located in the northwestern portion of the U.S. state of California. Trinity County is rugged, mountainous, heavily forested, and lies along the Trinity River (for which it is named) within the Salmon, Klamath Mountains, as well as a portion of the Scott, Trinity, and North Yolla Bolly Mountains. It is also one of three counties in California with no incorporated cities (the other two counties in California with that distinction are Alpine and Mariposa counties).

As of the 2020 census, the population was 16,112, making it the fifth least-populous county in California, and the least-populous of California's 27 original counties. The county seat and largest community is Weaverville.

Trinity County has a rich history of Native Americans: Tsnungwe including the South Fork Hupa and tł'oh-mitah-xwe, Chimariko, and Wintu.

The county takes its name from the Trinity River, which was in turn named in 1845 by Major Pierson B. Reading, who was under the mistaken impression that the river emptied into Trinidad Bay. Trinity is the English translation of Trinidad.

Trinity County was one of the original counties of California, created in 1850 at the time of statehood. Parts of the county were ceded to Klamath County in 1852 and to Humboldt County in 1853.

In the first half of the 1850s the California State Legislature established that the boundaries of Mendocino and Trinity Counties was the 40th parallel north. Both county board of supervisor's hired the surveyor W.H. Fauntleroy to survey the parallel, which he completed on October 30, 1872. The accuracy of the boundary was doubtful, and by 1891 the Mendocino County Board of Supervisors requested the California surveyor-general to survey the line and establish the boundaries between the two counties. The new line, as surveyed by Sam H. Rice and approved by the California Attorney General on December 18, 1891, was found to be two miles north of the common boundary surveyed by W.H. Fauntleroy, thereby resulting in Trinity County exercising jurisdiction two miles south of the 40th parallel north. Between 1891 and 1907, both counties claimed that the two mile wide strip of land belonged to themselves and not the other, with both counties attempting to levy and collect property tax land in said strip. In 1907, Trinity County sued Mendocino County in a Tehama County court to settle the dispute. The trial court in Tehama County ruled in favor of Trinity County, even though the land was situated south of the 40th parallel and state law stated that lands south of that parallel belonged to Mendocino County. The appellate court upheld the ruling of the trial court since Section 10 of the special act of March 30, 1872 (Stats. 1871-2, p. 766), which concerned this boundary and was the act under which Fauntleroy acted under, authorized the survey of the theretofore unknown location of the 40th parallel north, stated that "the lines run out, marked and defined as required by this act are hereby declared to be the true boundary lines of the counties named herein", thereby making the law in the political code which defined the boundary as the 40th parallel north only a suggestion and not a fact. The legislature subsequently affirmed this decision, with the modern statute defining the borders of the two counties referencing the survey of Fauntleroy as being the boundary between the two counties instead of the 40th parallel north.

According to the U.S. Census Bureau, the county has a total area of 3,208 square miles (8,310 km), of which 3,179 square miles (8,230 km) is land and 28 square miles (73 km) (0.9%) is water. The county contains a significant portion of Shasta-Trinity National Forest and the Trinity Alps Wilderness—the second largest wilderness in California.

Trinity County is made up of five census tracts. Census Tract 1.01 includes the communities of Douglas City, Lewiston, Trinity Center, and part of Coffee Creek and Weaverville. Notable features are Trinity Dam and Lake, Lewiston Dam and Lake, the Trinity River, and the Lewiston Valley. It has a population of 2585 people in 550 square miles, leading to a population density of 4.7 people per square mile. Census Tract 1.02 includes most of Weaverville and Coffee Creek. It is the most populous census tract in the county, with 4558 people. It has 449 square miles, leading to a population density of 10.2 people per square mile. Notable features are the Weaver Basin, the Trinity Alps, Scott Mountains, and the upper Trinity River. Census Tract 2 includes the Downriver area of Trinity County. This means the communities of Junction City, Big Flat, Big Bar, Burnt Ranch, Hawkins Bar, and Salyer. It includes 2024 people, and notable features are the Trinity River, the Trinity Alps, and the New River. Census Tract 3 includes the communities of Hayfork, Hyampom, and Wildwood. It has 3105 people in 600 square miles, leading to a population density of 5.2 people per square mile. Notable features are the South Fork of the Trinity River, South Fork Mountain, Hayfork Valley and Hayfork Creek, Hyampom Valley, Chanchellula Peak and Wilderness area, and Hayfork Bally. Census Tract 4 is the largest by area but the least populous census tract in the county with 975 people. It contains 833 square miles, leading to a population density of 1.2 people per square mile. The largest community by far is Mad River, with other smaller ones being Ruth, Kettenpom, and Zenia. Notable features include South Fork Mountain, the Mad River, the Van Duzen River, Ruth Lake, Ruth Valley, Kettenpom Valley, Hoaglin Valley, and Hettenshaw Valley.

The county hosts many visitors, especially during summer months, for camping, backpacking, boating on the lakes, rafting/kayaking on the rivers, hunting, and fishing. The summers tend to be clear, sunny, warm, and very dry, with little rain from June to September except for some mountain thunderstorms in the highest elevations. Summer days in the populated areas of the county range from 85 to 100 degrees, and summer nights range from 45 to 62 Winter days range from 35 to 50, and nights range from 18 to 35. The winters tend to have copious precipitation, increasing with elevation and falling mostly as rain under 1,000 m (3,300 ft) in the valley bottoms, and mostly as snow over 1,000 m (3,300 ft) on the mountainsides. December, January, and February are the wettest. The precipitation ranges from 30 to 35 inches at low elevations isolated from coastal influence, such as Big Bar, Hayfork, and Weaverville, up to 55 or 60 inches at high elevations, on the coastal side of South Fork Mountain, or where gaps in the mountain allow for precipitation to get through. Examples of this last phenomenon include Salyer and Forest Glen. Kalmia Lake, at nearly 7500 feet in the Canyon Creek area of the Trinity Alps, is reputed to be the snowiest place in California, outpacing Lake Helen in Mount Lassen National Park, which receives 600-700 inches of snow each winter. Average snowfall in the populated parts of the county ranges from 0-5 inches in the lower Trinity Valley to at least 100 inches in places above 4000 feet, such as Indian Valley west of Hayfork.

There is an extensive wild river and stream system, and the terrain is quite rugged and forested, with the highest point at Mount Eddy, over 9,000 ft (2,700 m). The Klamath Mountains occupy the vast portion of the county.

• Siskiyou County - north
• Shasta County - east
• Tehama County - southeast
• Mendocino County - south
• Humboldt County - west

• Shasta-Trinity National Forest (part)
• Six Rivers National Forest (part)
• Mendocino National Forest (part)
• Shasta-Trinity National Recreation Area (part)
• Trinity Alps Wilderness (part)
• Yolla Bolly-Middle Eel Wilderness (part)

Chancelulla Wilderness

Trinity County has a mediterranean climate with very warm, dry and sunny summer days and high diurnal temperature variation due to the cool nights. The hot afternoons form a stark contrast to the mild coastal climates of Humboldt County relatively nearby. Winters are chilly and wet. Below is climate normals from county seat Weaverville. There are different microclimates in the county as elevations vary.

Trinity was a Republican-leaning county in Presidential and congressional elections until recently; now it is a tossup. No Democrat had won the county since Jimmy Carter in 1976 until Barack Obama defeated John McCain by a 4% margin (50% to 46%) in 2008. In 2012, the county again voted Republican, but narrowly. Voter registration reflects this trend, with Democratic and Republican registration in a near dead heat (D: 2,710, R: 2,716). Third-party candidates tend to do rather well in Trinity County: George Wallace got over 13% of the county's vote in 1968, and it was the only California county carried by Ross Perot in 1992. It was also Perot's best performance in the state in 1996, although he didn't carry it again. John Anderson also did very well in 1980, as did third-party candidates in 2016.

Trinity County was the only California county where Obama won in 2008 and Joe Biden lost in 2020.

United States presidential election results for Trinity County, California

Year	Republican		Democratic		Third party(ies)
	No.	%	No.	%	No.	%
2024	2,979	52.47%	2,449	43.14%	249	4.39%
2020	3,188	50.36%	2,851	45.04%	291	4.60%
2016	2,812	48.62%	2,214	38.28%	758	13.11%
2012	2,716	47.33%	2,674	46.59%	349	6.08%
2008	2,940	45.72%	3,233	50.28%	257	4.00%
2004	3,560	54.66%	2,782	42.71%	171	2.63%
2000	3,340	57.62%	1,932	33.33%	525	9.06%
1996	2,530	42.93%	2,203	37.38%	1,160	19.68%
1992	1,886	31.28%	1,967	32.63%	2,176	36.09%
1988	3,267	54.63%	2,518	42.11%	195	3.26%
1984	3,544	59.71%	2,218	37.37%	173	2.91%
1980	3,048	54.96%	1,734	31.27%	764	13.78%
1976	1,989	45.66%	2,172	49.86%	195	4.48%
1972	1,868	50.75%	1,621	44.04%	192	5.22%
1968	1,426	43.12%	1,433	43.33%	448	13.55%
1964	1,252	36.41%	2,175	63.25%	12	0.35%
1960	1,418	38.35%	2,262	61.17%	18	0.49%
1956	1,447	50.42%	1,406	48.99%	17	0.59%
1952	1,697	57.14%	1,242	41.82%	31	1.04%
1948	975	45.08%	1,053	48.68%	135	6.24%
1944	567	42.22%	770	57.33%	6	0.45%
1940	780	34.79%	1,431	63.83%	31	1.38%
1936	655	30.87%	1,424	67.11%	43	2.03%
1932	318	21.09%	1,101	73.01%	89	5.90%
1928	447	48.85%	433	47.32%	35	3.83%
1924	336	36.48%	154	16.72%	431	46.80%
1920	622	62.89%	285	28.82%	82	8.29%
1916	424	35.16%	661	54.81%	121	10.03%
1912	1	0.10%	461	46.29%	534	53.61%
1908	393	44.41%	331	37.40%	161	18.19%
1904	467	54.11%	308	35.69%	88	10.20%
1900	544	52.36%	485	46.68%	10	0.96%
1896	502	46.44%	545	50.42%	34	3.15%
1892	495	50.82%	457	46.92%	22	2.26%

Trinity County is in California's 2nd congressional district, represented by Democrat Jared Huffman.

In the state legislature Trinity is in the 2nd Senate District, represented by Democrat Mike McGuire, and the 2nd Assembly District, represented by Democrat Chris Rogers.

In 2010, Trinity County voted against Proposition 19, which would have taxed and regulated marijuana.

In 2016 Trinity County residents were asked again to vote on legalization of state-level recreational marijuana, facilitated by the Adult Use of Marijuana Act (AUMA), also known as California Proposition 64. The measure passed with 50.1% in favor of legalization. Statewide, the measure passed with 57.1% of the vote.

Population and registered voters
Total population	13,711
Registered voters	7,846	57.2%
Democratic	2,630	33.5%
Republican	2,695	34.3%
Democratic–Republican spread	-65	-0.8%
Independent	376	4.8%
Green	126	1.6%
Libertarian	93	1.2%
Peace and Freedom	33	0.4%
Americans Elect	0	0.0%
Other	100	1.3%
No party preference	1,793	22.9%

• State Route 299
• State Route 3
• State Route 36

Trinity Transit provides weekday intercity bus service on State Routes 3 and 299, with connecting service in Willow Creek and the Redding Amtrak station. Service is also provided from Weaverville to Lewiston (MWF) and Hayfork (daily).

The county owns five general aviation airports: Trinity Center Airport, Weaverville Airport, Hayfork Airport, Hyampom Airport and Ruth Airport. The closest major airport is in Sacramento.

The following table includes the number of incidents reported and the rate per 1,000 persons for each type of offense.

Population and crime rates
Population	13,711
Violent crime	22	1.60
Homicide	0	0.00
Forcible rape	0	0.00
Robbery	3	0.22
Aggravated assault	19	1.39
Property crime	123	8.97
Burglary	60	4.38
Larceny-theft	66	4.81
Motor vehicle theft	26	1.90
Arson	0	0.00

Trinity County, California – Racial and ethnic composition
Note: the US Census treats Hispanic/Latino as an ethnic category. This table excludes Latinos from the racial categories and assigns them to a separate category. Hispanics/Latinos may be of any race.

Race / Ethnicity (NH = Non-Hispanic)	Pop 2000	Pop 2010	Pop 2020	% 2000	% 2010	% 2020
White alone (NH)	11,271	11,518	11,374	86.55%	83.55%	70.59%
Black or African American alone (NH)	54	45	66	0.41%	0.33%	0.41%
Native American or Alaska Native alone (NH)	583	558	416	4.48%	4.05%	2.58%
Asian alone (NH)	58	93	2,212	0.45%	0.67%	13.73%
Pacific Islander alone (NH)	15	16	24	0.12%	0.12%	0.15%
Other Race alone (NH)	13	20	106	0.10%	0.15%	0.66%
Mixed race or Multiracial (NH)	511	577	977	3.92%	4.19%	6.06%
Hispanic or Latino (any race)	517	959	937	3.97%	6.96%	5.82%
Total	13,022	13,786	16,112	100.00%	100.00%	100.00%

Population, race, and income
Total population	13,711
White	12,201	89.0%
Black or African American	53	0.4%
American Indian or Alaska Native	237	1.7%
Asian	158	1.2%
Native Hawaiian or other Pacific Islander	40	0.3%
Some other race	130	0.9%
Two or more races	892	6.5%
Hispanic or Latino (of any race)	924	6.7%
Per capita income	$22,551
Median household income	$37,672
Median family income	$46,980

Places by population and race
Place	Type	Population	White	Other	Asian	Black or African American	Native American	Hispanic or Latino (of any race)
Burnt Ranch	CDP	293	92.8%	6.1%	0.0%	0.0%	1.0%	2.0%
Coffee Creek	CDP	219	96.3%	3.7%	0.0%	0.0%	0.0%	3.7%
Douglas City	CDP	647	87.6%	10.7%	1.4%	0.0%	0.3%	5.6%
Hayfork	CDP	2,300	83.9%	10.9%	3.6%	0.0%	1.6%	7.7%
Hyampom	CDP	250	71.1%	28.9%	0.0%	0.0%	0.0%	0.0%
Junction City	CDP	955	96.1%	3.4%	0.0%	0.0%	0.5%	5.1%
Lewiston	CDP	1,391	89.1%	6.8%	0.0%	0.0%	4.1%	5.6%
Mad River	CDP	391	90.8%	2.3%	0.0%	0.0%	6.9%	1.8%
Ruth	CDP	144	100.0%	0.0%	0.0%	0.0%	0.0%	0.0%
Trinity Center	CDP	173	100.0%	0.0%	0.0%	0.0%	0.0%	0.0%
Trinity Village	CDP	163	100.0%	0.0%	0.0%	0.0%	0.0%	0.0%
Weaverville	CDP	3,703	92.1%	6.3%	0.0%	0.5%	1.1%	11.4%

Places by population and income
Place	Type	Population	Per capita income	Median household income	Median family income
Burnt Ranch	CDP	293	$35,310	$28,929	$52,188
Coffee Creek	CDP	219	$27,940	$55,714	$36,607
Douglas City	CDP	647	$32,114	$41,042	$51,667
Hayfork	CDP	2,300	$18,017	$37,333	$52,976
Hyampom	CDP	250	$13,598	$25,729	$27,000
Junction City	CDP	955	$17,128	$36,250	$41,250
Lewiston	CDP	1,391	$23,990	$44,375	$50,250
Mad River	CDP	391	$13,773	$23,813	$52,589
Ruth	CDP	144	$24,099	$51,250	$73,000
Trinity Center	CDP	173	$24,619	$26,563	$28,125
Trinity Village	CDP	163	$15,528	$23,315	$23,438
Weaverville	CDP	3,703	$24,714	$42,337	$47,135

The 2010 United States Census reported that Trinity County had a population of 13,786. The racial makeup of Trinity County was 12,033 (87.3%) White, 59 (0.4%) African American, 655 (4.8%) Native American, 94 (0.7%) Asian, 16 (0.1%) Pacific Islander, 217 (1.6%) from other races, and 712 (5.2%) from two or more races. Hispanic or Latino of any race were 959 persons (7.0%).

Population reported at 2010 United States Census
The County	Total Population	White	African American	Native American	Asian	Pacific Islander	other races	two or more races	Hispanic or Latino (of any race)
Trinity County	13,786	12,033	59	655	94	16	217	712	959
Census-designated places	Total Population	White	African American	Native American	Asian	Pacific Islander	other races	two or more races	Hispanic or Latino (of any race)
Burnt Ranch	281	241	0	15	4	0	1	20	19
Coffee Creek	217	198	0	5	5	0	3	6	16
Douglas City	713	639	0	22	8	2	13	29	47
Hayfork	2,368	1,999	4	162	8	2	38	155	189
Hyampom	241	199	0	20	0	0	7	15	19
Junction City	680	597	1	29	2	0	20	31	49
Lewiston	1,193	1,074	8	37	6	5	21	42	78
Mad River	420	383	1	11	1	0	7	17	21
Ruth	195	170	0	9	1	0	1	14	2
Trinity Center	267	249	0	7	1	3	2	5	11
Trinity Village	297	269	1	18	0	0	0	9	4
Weaverville	3,600	3,162	11	152	41	1	38	195	255
Other unincorporated areas	Total Population	White	African American	Native American	Asian	Pacific Islander	other races	two or more races	Hispanic or Latino (of any race)
All others not CDPs (combined)	3,314	2,853	33	168	17	3	66	174	249

Historical population

Census	Pop.	Note	%±
1850	1,635		—
1860	5,125		213.5%
1870	3,213		−37.3%
1880	4,999		55.6%
1890	3,719		−25.6%
1900	4,383		17.9%
1910	3,301		−24.7%
1920	2,551		−22.7%
1930	2,809		10.1%
1940	3,970		41.3%
1950	5,087		28.1%
1960	9,706		90.8%
1970	7,615		−21.5%
1980	11,858		55.7%
1990	13,063		10.2%
2000	13,022		−0.3%
2010	13,786		5.9%
2020	16,112		16.9%
2023 (est.)	15,670		−2.7%
U.S. Decennial Census 1790-1960 1900-1990 1990-2000 2010-2020

This section needs to be updated. The reason given is: Newer information is available from the 2010 and 2020 Census reports. Please help update this article to reflect recent events or newly available information. (December 2021)

As of the census of 2000, there were 13,022 people, 5,587 households, and 3,625 families residing in the county. The population density was 4 people per square mile (1.5 people/km). There were 7,980 housing units at an average density of 2 units per square mile (0.77 units/km). The racial makeup of the county was 88.9% White, 0.5% Black or African American, 4.9% Native American, 0.5% Asian, 0.1% Pacific Islander, 0.9% from other races, and 4.4% from two or more races. 4.0% of the population were Hispanic or Latino of any race. 16.1% were of German, 13.4% English, 12.1% Irish and 9.5% American ancestry according to Census 2000. 97.3% spoke English and 1.8% Spanish as their first language.

There were 5,587 households, out of which 25.4% had children under the age of 18 living with them, 50.5% were married couples living together, 10.1% had a female householder with no husband present, and 35.1% were non-families. 29.5% of all households were made up of individuals, and 11.1% had someone living alone who was 65 years of age or older. The average household size was 2.29 and the average family size was 2.80.

In the county, the population was spread out, with 22.8% under the age of 18, 5.1% from 18 to 24, 22.7% from 25 to 44, 32.1% from 45 to 64, and 17.2% who were 65 years of age or older. The median age was 45 years. For every 100 females there were 104.2 males. For every 100 females age 18 and over, there were 102.6 males.

The median income for a household in the county was $27,711, and the median income for a family was $34,343. Males had a median income of $31,131 versus $24,271 for females. The per capita income for the county was $16,868. About 14.1% of families and 18.7% of the population were below the poverty line, including 26.2% of those under age 18 and 7.2% of those age 65 or over.

City	Year incorporated	Year dissolved	Fate
Helena, California	1851	1950s	Became private property
Canon City, California	1851	1891	Nothing remains of the former town but a historical marker.
Dedrick, California	1890	1941	Nothing remains of the former town but a historical marker.
Deadwood, Trinity County, California	1881	1915	Nothing remains of the former town.

K-12 school districts include:

Unified:

Elementary:

The population ranking of the following table is based on the 2020 census of Trinity County.

† county seat

Rank	City/Town/etc.	Municipal type	Population (2020 Census)
1	† Weaverville	CDP	3,667
2	Post Mountain	CDP	3,032
3	Hayfork	CDP	2,324
4	Lewiston	CDP	1,222
5	Douglas City	CDP	868
6	Junction City	CDP	658
7	Round Valley Reservation (partially in Mendocino County)	AIAN	454
8	Salyer	CDP	389
9	Mad River	CDP	361
10	Trinity Village	CDP	278
11	Ruth	CDP	254
12	Burnt Ranch	CDP	250
13	Hyampom	CDP	241
14	Trinity Center	CDP	198
15	Coffee Creek	CDP	152

• Hiking trails in Trinity County
• National Register of Historic Places listings in Trinity County, California
• Trinity Lakes American Viticultural Area
• Willow Creek American Viticultural Area

• Official website
• VisitTrinity: Visitors Bureau
• Trinity County Chamber Of Commerce
• Tsnungwe Official Website
• Expose Trinity County

40°40′N 123°07′W / 40.66°N 123.12°W / 40.66; -123.12