Colusa County (/kəˈluːsə/ ) is a county located in the U.S. state of California. As of the 2020 census, the population was 21,839. The county seat is Colusa. It is in the northern Sacramento Valley, northwest of the state capital, Sacramento.

Colusa County is one of the original counties of California, created in 1850 at the time of statehood. Parts of the county's territory were given to Tehama County in 1856 and to Glenn County in 1891.

The county was named after the 1844 Rancho Colus Mexican land grant to John Bidwell. The name of the county in the original state legislative act of 1850 was spelled Colusi, and often in newspapers was spelled Coluse. The word is derived from the name of a Patwin village known as Ko'-roo or Korusi located on the west side of the Sacramento River on the site of the present-day city of Colusa. The name was established as Colusa by 1855.

Present-day Colusa County was originally home to the Patwin band of the Wintun people, whose territory included areas along the Sacramento River as well as lands extending west towards Lake County, bounded in the north by the sources of Stony Creek near Stonyford and in the south by Putah Creek.

Linguistically, the Patwin people in the Colusa area spoke two dialects of the Southern Wintuan language. River Patwin was spoken in villages along the Sacramento River, including at Korusi, site of the present city of Colusa. Hill Patwin was spoken in the plains and foothills to the west.

Present-day Colusa County was included as part of three Mexican land grants: John Bidwell's smaller 1845 Rancho Colus grant, which included the modern city of Colusa; the larger 1844 Rancho Jimeno grant, which surrounded the Colus grant; and the 1844 Larkin's Children grant, located upriver from Colusa near the present town of Princeton, California.

According to the U.S. Census Bureau, the county has a total area of 1,156 square miles (2,990 km), of which 1,151 square miles (2,980 km) is land and 5.6 square miles (15 km) (0.5%) is water. A large number of streams drain the county, including Elk Creek, Salt Creek, Stony Creek and Bear Creek.

The county's eastern boundary is formed, in part, by the Sacramento River.

• Glenn County - north
• Butte County - northeast
• Sutter County - east
• Yolo County - south
• Lake County - west

• Butte Sink National Wildlife Refuge (part)
• Colusa National Wildlife Refuge
• Delevan National Wildlife Refuge
• Mendocino National Forest (part)
• Sacramento National Wildlife Refuge (part)

Historical population

Census	Pop.	Note	%±
1850	115		—
1860	2,274		1,877.4%
1870	6,165		171.1%
1880	13,118		112.8%
1890	14,640		11.6%
1900	7,364		−49.7%
1910	7,732		5.0%
1920	9,290		20.2%
1930	10,258		10.4%
1940	9,788		−4.6%
1950	11,651		19.0%
1960	12,075		3.6%
1970	12,430		2.9%
1980	12,791		2.9%
1990	16,275		27.2%
2000	18,804		15.5%
2010	21,419		13.9%
2020	21,839		2.0%
2023 (est.)	22,037		0.9%
U.S. Decennial Census 1790–1960 1900–1990 1990–2000 2010 2020

Colusa 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)	9,018	8,524	6,941	47.96%	39.80%	31.78%
Black or African American alone (NH)	88	168	182	0.47%	0.78%	0.83%
Native American or Alaska Native alone (NH)	316	296	280	1.68%	1.38%	1.28%
Asian alone (NH)	220	267	252	1.17%	1.25%	1.15%
Pacific Islander alone (NH)	67	59	70	0.36%	0.28%	0.32%
Other Race alone (NH)	34	29	92	0.18%	0.14%	0.42%
Mixed Race or Multi-Racial (NH)	309	272	546	1.64%	1.27%	2.50%
Hispanic or Latino (any race)	8,752	11,804	13,476	46.54%	55.11%	61.71%
Total	18,804	21,419	21,839	100.00%	100.00%	100.00%

Population, race, and income
Total population	21,297
White	14,491	68.0%
Black or African American	203	1.0%
American Indian or Alaska Native	288	1.4%
Asian	252	1.2%
Native Hawaiian or other Pacific Islander	41	0.2%
Some other race	4,893	23.0%
Two or more races	1,129	5.3%
Hispanic or Latino (of any race)	11,460	53.8%
Per capita income	$21,271
Median household income	$49,558
Median family income	$55,063

Places by population and race
Place	Type	Population	White	Other	Asian	Black or African American	Native American	Hispanic or Latino (of any race)
Arbuckle	CDP	3,236	55.3%	43.9%	0.5%	0.0%	0.3%	66.0%
College City	CDP	70	100.0%	0.0%	0.0%	0.0%	0.0%	35.7%
Colusa	City	5,951	62.2%	32.2%	1.9%	0.9%	2.8%	56.4%
Grimes	CDP	517	64.2%	35.8%	0.0%	0.0%	0.0%	81.8%
Lodoga	CDP	185	85.4%	5.9%	0.0%	4.3%	4.3%	0.0%
Maxwell	CDP	1,144	77.4%	22.2%	0.3%	0.0%	0.0%	65.2%
Princeton	CDP	209	92.8%	2.9%	0.0%	0.0%	4.3%	7.7%
Stonyford	CDP	104	99.0%	0.0%	0.0%	1.0%	0.0%	0.0%
Williams	City	5,003	65.0%	32.7%	0.7%	1.0%	0.7%	74.3%

Places by population and income
Place	Type	Population	Per capita income	Median household income	Median family income
Arbuckle	CDP	3,236	$16,604	$48,878	$52,708
College City	CDP	70	$37,704	$62,750	$64,750
Colusa	City	5,951	$21,811	$49,100	$51,667
Grimes	CDP	517	$9,984	$30,897	$31,058
Lodoga	CDP	185	$25,004	$24,881	$65,500
Maxwell	CDP	1,144	$16,454	$43,036	$44,405
Princeton	CDP	209	$28,005	$58,571	$60,000
Stonyford	CDP	104	$21,163	$33,750	$49,250
Williams	City	5,003	$14,974	$47,934	$52,303

The 2010 United States census reported that Colusa County had a population of 21,419. The racial makeup of Colusa County was 13,854 (64.7%) White, 195 (0.9%) African American, 419 (2.0%) Native American, 281 (1.3%) Asian, 68 (0.3%) Pacific Islander, 5,838 (27.3%) from other races, and 764 (3.6%) from two or more races. Hispanic or Latino of any race were 11,804 persons (55.1%).

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)
Colusa County	21,419	13,854	195	419	281	68	5,838	764	11,804
Incorporated cities	Total Population	White	African American	Native American	Asian	Pacific Islander	other races	two or more races	Hispanic or Latino (of any race)
Colusa	5,971	3,944	54	107	80	28	1,510	248	3,128
Williams	5,123	2,785	59	55	94	4	1,946	180	3,891
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)
Arbuckle	3,028	1,746	18	23	18	5	1,124	94	2,116
College City	290	207	0	5	1	0	51	26	134
Grimes	391	284	7	3	1	0	65	31	258
Lodoga	197	167	16	4	2	2	3	3	8
Maxwell	1,103	734	11	14	9	2	306	27	570
Princeton	303	217	0	10	1	1	70	4	93
Stonyford	149	127	0	4	0	1	12	5	22
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)	4,864	3,643	30	194	75	25	751	146	1,584

As of the census of 2000, there were 18,804 people, 6,097 households, and 4,578 families residing in the county. The population density was 16 people per square mile (6.2 people/km). There were 6,774 housing units at an average density of 6 per square mile (2.3/km). The racial makeup of the county was 64.3% White, 0.6% Black or African American, 2.3% Native American, 1.2% Asian, 0.4% Pacific Islander, 26.7% from other races, and 4.5% from two or more races. 46.5% of the population were Hispanic or Latino of any race. 8.5% were of German, 5.6% English, 5.5% American and 5.4% Irish ancestry according to Census 2000. 58.7% spoke English and 40.4% Spanish as their first language.

There were 6,097 households, out of which 41.4% had children under the age of 18 living with them, 59.6% were married couples living together, 9.6% had a female householder with no husband present, and 24.9% were non-families. 21.5% of all households were made up of individuals, and 10.1% had someone living alone who was 65 years of age or older. The average household size was 3.01 and the average family size was 3.51.

In the county, the population was spread out, with 31.6% under the age of 18, 10.3% from 18 to 24, 26.9% from 25 to 44, 19.8% from 45 to 64, and 11.4% who were 65 years of age or older. The median age was 32 years. For every 100 females there were 103.4 males. For every 100 females age 18 and over, there were 103.8 males.

The median income for a household in the county was $35,062, and the median income for a family was $40,138. Males had a median income of $32,210 versus $21,521 for females. The per capita income for the county was $14,730. About 13.0% of families and 16.1% of the population were below the poverty line, including 19.5% of those under age 18 and 8.2% of those age 65 or over.

Population and registered voters
Total eligible population	13,214
Registered voters	10,144	76.7%
Democratic	3,214	24.3%
Republican	4,062	30.7%
Democratic–Republican spread	-848	-6.4%
American Independent	376	2.8%
Libertarian	141	1.0%
Green	29	0.2%
Peace and Freedom	64	0.4%
Unknown	2	0.0%
Other	17	0.1%
No party preference	2,239	16.9%

Cities by population and voter registration
City	Population	Registered voters	Democratic	Republican	D–R spread	Other	No party preference
Colusa	5,951	37.8%	35.5%	44.6%	-9.1%	5.6%	16.8%
Williams	5,003	22.7%	43.5%	31.4%	+12.1%	3.1%	23.0%

In its early history Colusa was one of the most reliable Democratic counties in California. Along with Mariposa County, it was one of only two counties in the Pacific States to support Alton B. Parker in 1904. From 1880 until 1952, Colusa only went Republican during the GOP landslides of the Roaring Twenties. Since 1952, however, Colusa has become a strongly Republican county in Presidential and congressional elections, with Lyndon Johnson, in 1964, being the last Democrat to win the county.

United States presidential election results for Colusa County, California

Year	Republican		Democratic		Third party(ies)
	No.	%	No.	%	No.	%
2024	4,414	62.87%	2,431	34.62%	176	2.51%
2020	4,559	57.27%	3,239	40.69%	163	2.05%
2016	3,551	53.02%	2,661	39.73%	485	7.24%
2012	3,601	59.57%	2,314	38.28%	130	2.15%
2008	3,733	57.89%	2,569	39.84%	146	2.26%
2004	4,142	67.17%	1,947	31.58%	77	1.25%
2000	3,629	64.92%	1,745	31.22%	216	3.86%
1996	3,047	54.29%	2,054	36.60%	511	9.11%
1992	2,589	45.94%	1,798	31.91%	1,248	22.15%
1988	3,077	59.49%	2,022	39.10%	73	1.41%
1984	3,388	65.30%	1,725	33.25%	75	1.45%
1980	2,897	58.00%	1,605	32.13%	493	9.87%
1976	2,733	52.74%	2,340	45.16%	109	2.10%
1972	2,715	57.56%	1,810	38.37%	192	4.07%
1968	2,361	51.58%	1,858	40.59%	358	7.82%
1964	1,811	39.32%	2,790	60.57%	5	0.11%
1960	2,497	51.37%	2,348	48.30%	16	0.33%
1956	2,474	53.23%	2,171	46.71%	3	0.06%
1952	2,824	59.81%	1,881	39.83%	17	0.36%
1948	1,803	46.22%	2,020	51.78%	78	2.00%
1944	1,579	42.92%	2,090	56.81%	10	0.27%
1940	1,774	39.74%	2,655	59.48%	35	0.78%
1936	1,186	28.15%	2,965	70.38%	62	1.47%
1932	1,095	27.50%	2,752	69.11%	135	3.39%
1928	1,752	56.30%	1,338	42.99%	22	0.71%
1924	1,127	43.84%	495	19.25%	949	36.91%
1920	1,645	61.24%	907	33.77%	134	4.99%
1916	1,011	31.82%	1,998	62.89%	168	5.29%
1912	3	0.11%	1,760	63.58%	1,005	36.31%
1908	730	38.58%	1,064	56.24%	98	5.18%
1904	885	46.78%	900	47.57%	107	5.66%
1900	648	35.98%	1,075	59.69%	78	4.33%
1896	581	30.86%	1,250	66.38%	52	2.76%
1892	645	31.08%	1,187	57.20%	243	11.71%

Colusa County is in California's 1st congressional district, represented by Republican Doug LaMalfa.

In the State Assembly, Colusa County is split between the 3rd and 4th districts, represented by Republican James Gallagher and Democrat Cecilia Aguiar-Curry, respectively. In the State Senate, the county is in the 4th Senate District, represented by Republican Marie Alvarado-Gil.

On November 4, 2008, Colusa County voted 71.6% for Proposition 8 which amended the California Constitution to ban same-sex marriages.

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	21,297
Violent crime	59	2.77
Homicide	1	0.05
Forcible rape	13	0.61
Robbery	8	0.38
Aggravated assault	37	1.74
Property crime	352	16.53
Burglary	197	9.25
Larceny-theft	293	13.76
Motor vehicle theft	37	1.74
Arson	3	0.14

Cities by population and crime rates
City	Population	Violent crimes	Violent crime rate per 1,000 persons	Property crimes	Property crime rate per 1,000 persons
Colusa	6,065	11	1.81	170	28.03
Williams	5,200	9	1.73	76	14.62

• Interstate 5
• State Route 16
• State Route 20
• State Route 45

Colusa County Transit runs buses from Colusa to Williams, Arbuckle, Grimes and College City, with limited service to Maxwell.

Colusa County Airport is a general-aviation airport located near the city of Colusa. The closest major airport is in Sacramento.

• Colusa (county seat)
• Williams

• Arbuckle
• College City
• Grimes
• Lodoga
• Maxwell
• Princeton
• Stonyford

• Sites

The population ranking of the following table is based on the 2010 census of Colusa County.

† county seat

Rank	City/Town/etc.	Municipal type	Population (2010 Census)
1	† Colusa	City	5,971
2	Williams	City	5,123
3	Arbuckle	CDP	3,028
4	Maxwell	CDP	1,103
5	Grimes	CDP	391
6	Princeton	CDP	303
7	College City	CDP	290
8	Lodoga	CDP	197
9	Stonyford	CDP	149
10	Colusa Rancheria	AIAN	76
11	Cortina Rancheria	AIAN	21

California Historical Landmarks in Colusa County:

• Colusa County Courthouse built in 1861,.
• Letts Valley settled in 1855 by Jack and David Lett. Marker at Letts Lake Campground at Letts Lake.
• Swift's Stone Corral, built by Granville P. Swift in 1850.

• List of school districts in Colusa County, California
• National Register of Historic Places listings in Colusa County, California
• Thomas D. Harp, mentions 1891 division of the county

• Official website
• Colusa County Sun Herald
• Colusa County Guide

39°11′N 122°14′W / 39.18°N 122.24°W / 39.18; -122.24