Benton County is one of the 36 counties in the U.S. state of Oregon. As of the 2023 census population estimates, the population was 99,355. Its county seat is Corvallis. The county was named after Thomas Hart Benton, a U.S. Senator who advocated American control over the Oregon Country. Benton County is designated as the Corvallis, OR Metropolitan Statistical Area, which is included in the Portland–Vancouver–Salem, OR–WA Combined Statistical Area. It is in the Willamette Valley.

Benton County was created on December 23, 1847, by an act of the Provisional Government of Oregon. The county was named after Democratic Senator Thomas Hart Benton of Missouri, an advocate of the doctrine of Manifest Destiny and the belief that the American government should control the whole of the Oregon Country. At the time of its formation the county included all the country west of the Willamette River, south of Polk County and running all the way to the California border in the south and the Pacific Ocean in the west.

The county was created out of lands originally inhabited by the Klickitat, who rented it from the Kalapuyas for use as hunting grounds. All aboriginal claims to land within Benton County were ceded in the Treaty of Dayton in 1855. Portions of Benton County were taken to form Coos, Curry, Douglas, Jackson, Josephine, Lane and Lincoln Counties, leaving Benton County in its present form.

The city of Marysville, later renamed Corvallis, was made the county seat in 1851. The city briefly was the capital of Oregon. In 1862 Corvallis became the site of the Oregon State Agricultural College, known today as Oregon State University.

According to the United States Census Bureau, the county has a total area of 679 square miles (1,760 km), of which 676 square miles (1,750 km) is land and 2.7 square miles (7.0 km) (0.4%) is water. It is the fourth-smallest county in Oregon by land area and third-smallest by total area.

• Polk County (north)
• Lincoln County (west)
• Linn County (east)
• Lane County (south)

• Siuslaw National Forest (part)
• William L. Finley National Wildlife Refuge

Historical population

Census	Pop.	Note	%±
1850	814		—
1860	3,074		277.6%
1870	4,584		49.1%
1880	6,403		39.7%
1890	8,650		35.1%
1900	6,706		−22.5%
1910	10,663		59.0%
1920	13,744		28.9%
1930	16,555		20.5%
1940	18,629		12.5%
1950	31,570		69.5%
1960	39,165		24.1%
1970	53,776		37.3%
1980	68,211		26.8%
1990	70,811		3.8%
2000	78,153		10.4%
2010	85,579		9.5%
2020	95,184		11.2%
2023 (est.)	97,713		2.7%
U.S. Decennial Census 1790–1960 1900–1990 1990–2000 2010–2020

As of the 2020 census, there were 95,184 people, the racial make up of the county was 75.9% non-Hispanic white, 1% African American, 0.6% Native American, 6.7% Asian, 6.1% of two or more races. Residents of Hispanic or Latino ancestry made up 9% of the population.

As of the 2010 census, there were 85,579 people, 34,317 households, and 19,256 families residing in the county. The population density was 126.6 inhabitants per square mile (48.9 inhabitants/km). There were 36,245 housing units at an average density of 53.6 units per square mile (20.7 units/km). The racial makeup of the county was 87.1% white, 5.2% Asian, 0.9% black or African American, 0.7% American Indian, 0.2% Pacific islander, 2.3% from other races, and 3.6% from two or more races. Those of Hispanic or Latino origin made up 6.4% of the population. In terms of ethnicity, 22.6% reported German ancestry, 16.1% English, 13.5% Irish, and 3.6% were American heritage.

Of the 34,317 households, 24.2% had children under the age of 18 living with them, 45.3% were married couples living together, 7.3% had a female householder with no husband present, 43.9% were non-families, and 28.2% of all households were made up of individuals. The average household size was 2.35 and the average family size was 2.87. The median age was 32.1 years.

The median income for a household in the county was $48,012 and the median income for a family was $71,763. Males had a median income of $50,282 versus $35,387 for females. The per capita income for the county was $26,177. About 7.7% of families and 19.1% of the population were below the poverty line, including 13.6% of those under age 18 and 5.5% of those age 65 or over.

As of the 2000 census, there were 78,153 people, 30,145 households, and 18,237 families residing in the county. The population density was 116 people per square mile (45 people/km). There were 31,980 housing units at an average density of 47 units per square mile (18/km). The racial makeup of the county was 89.16% White, 0.84% Black or African American, 0.79% Native American, 4.49% Asian, 0.24% Pacific Islander, 1.92% from other races, and 2.56% from two or more races. 4.66% of the population were Hispanic or Latino of any race. 18.2% were of German, 11.6% English, 8.9% Irish and 7.0% American ancestry. 91.1% spoke English, 4.1% Spanish and 1.0% Chinese as their first language.

There were 30,145 households, out of which 28.40% had children under the age of 18 living with them, 50.40% were married couples living together, 7.20% had a female householder with no husband present, and 39.50% were non-families. 26.10% of all households were made up of individuals, and 6.70% had someone living alone who was 65 years of age or older. The average household size was 2.43 and the average family size was 2.95.

In the county, 21.30% of the population was under the age of 18, 20.20% was from 18 to 24, 26.70% from 25 to 44, 21.40% from 45 to 64, and 10.30% was 65 years of age or older. The median age was 31 years. For every 100 females there were 99.10 males. For every 100 females age 18 and over, there were 97.80 males.

The median income for a household in the county was $41,897, and the median income for a family was $56,319. Males had a median income of $42,018 versus $29,795 for females. The per capita income for the county was $21,868. About 6.80% of families and 14.60% of the population were below the poverty line, including 10.60% of those under age 18 and 4.90% of those age 65 or over.

Benton County has the lowest church attendance per capita of any county in the nation (25% attendance).

City / Community	Population (As of 2023)
Corvallis	61,087
North Albany	11,273
Philomath	5,838
Adair Village	1,018
Monroe	763
Lewisburg	569
Mary’s River Estates	400
Crescent Valley	336
Vineyard Mountain	321
Country Estates	259
Alpine	258
Palestine	223
Alsea	220
Asbahr-Pilkington	191
Chinook	182
Dry Creek	178
Summit	177
Kings Valley	147
Wren	134
Nash	130
Flynn	128
Cascade View	113
Hope	107
Ridgewood	103
McDonald Forest Estates	90
Rosewood Estates	88
Greenberry	88
Caldwell Hills	84
Panoramic Acres	84
Bellfountain	78
Oakwood Heights	76
Noon	76
Raguse	72
Merloy-Steele	68
Pheasant Meadows	64
Harris	64
Blodgett	58
Dawnwood	56
Brownly-Marshall	56
Hawk Crest	48
Green Acres	46
Hoskins	46
West Hills Acres	40
Lobster Valley	40
Hidden Valley	36
Glenbrook	32
Nashville	32
Alder	32
Kopplein	26
Country Hills	24
Dawson	20

• Adair Village
• Albany (part)
• Corvallis (county seat)
• Monroe
• Philomath

• Alpine
• Alsea
• Bellfountain
• Blodgett
• Kings Valley
• Summit

For a long time, Benton County strongly favored the Republican Party due to its significant Yankee influence. In the 1932 presidential election, it was the only county in the state to vote for Herbert Hoover instead of FDR. Along with Riverside County in California, it was one of only two counties in the Pacific States to be held by Hoover that year. As late as 1960, Benton was the most Republican county in the traditionally Republican state of Oregon, which at that point had never supported a Democrat other than FDR for president, except for 1912 when the Republican Party was divided and a very narrow victory in 1868. Up to 1984, Benton County had voted for a Democratic presidential candidate only four times, in the above-mentioned 1868 election plus the national Democratic landslides of 1912, 1936, and 1964. In 1964, Lyndon Johnson became the first Democrat to win an absolute majority of the county's vote since Horatio Seymour.

The Republican edge in the county narrowed from the 1970s onward, culminating when it swung from a five-point victory for Ronald Reagan in 1984 to a nine-point victory for Michael Dukakis in 1988. Since then, Benton County has become a strongly Democratic county, and is usually the second-strongest Democratic bastion in the state, behind only Multnomah County (Portland). This is largely due to the leanings of Oregon State's student body and staff, closely tracking with Democratic gains in other counties influenced by college towns. No Republican has come within nine percentage points of carrying Benton County since 1988, and Barack Obama, Hillary Clinton, and Joe Biden have won the county by over thirty percentage points during each of the last four presidential elections. Overall, Benton County is a reliable state bellwether, having voted for Oregon's statewide winner in every presidential election since 1948, along with Hood River County.

Since 1972, Benton County has been a home rule county, meaning that the citizens have full control over the county charter, rather than using a standard charter issued by the state. The voters have chosen to eliminate the traditional elected county offices of Assessor, Treasurer, Surveyor, Justice of the Peace, and Clerk. Currently, they only elect three County Commissioners and a Sheriff.

The three current Benton County Commissioners are Chair Pat Malone, Xanthippe Augerot, and Nancy Wyse. They are all members of the Democratic Party and have served since 2019, 2017, and 2021; respectively. Wyse and Augerot's current terms expire in January 2025, while Malone's is up in January 2023.

The current Benton County Sheriff is Jef Van Arsdall. He was appointed to the office in March 2021 to fill the remainder of the term of retiring sheriff Scott Jackson.

Benton County is currently one of 11 counties in Oregon in which therapeutic psilocybin is legal.

United States presidential election results for Benton County, Oregon

Year	Republican		Democratic		Third party(ies)
	No.	%	No.	%	No.	%
2020	14,878	28.18%	35,827	67.86%	2,094	3.97%
2016	13,445	27.58%	29,193	59.88%	6,115	12.54%
2012	14,991	33.46%	27,776	62.00%	2,035	4.54%
2008	15,264	32.84%	29,901	64.33%	1,313	2.82%
2004	18,460	40.36%	26,515	57.98%	760	1.66%
2000	15,825	41.40%	19,444	50.87%	2,957	7.74%
1996	12,450	36.09%	17,211	49.89%	4,839	14.03%
1992	11,550	30.46%	17,966	47.37%	8,407	22.17%
1988	14,004	44.30%	16,930	53.56%	676	2.14%
1984	17,836	52.36%	16,073	47.19%	153	0.45%
1980	14,982	43.42%	13,150	38.11%	6,375	18.47%
1976	15,555	53.08%	11,887	40.56%	1,865	6.36%
1972	14,906	56.34%	10,842	40.98%	708	2.68%
1968	11,654	61.29%	6,538	34.38%	824	4.33%
1964	7,250	43.98%	8,971	54.42%	265	1.61%
1960	9,734	64.36%	5,391	35.64%	0	0.00%
1956	9,016	68.15%	4,214	31.85%	0	0.00%
1952	9,229	75.27%	2,966	24.19%	67	0.55%
1948	6,839	66.21%	3,135	30.35%	355	3.44%
1944	5,242	64.39%	2,830	34.76%	69	0.85%
1940	5,089	62.99%	2,942	36.42%	48	0.59%
1936	3,390	45.67%	3,547	47.78%	486	6.55%
1932	4,068	54.73%	3,121	41.99%	244	3.28%
1928	4,605	75.55%	1,412	23.17%	78	1.28%
1924	3,417	60.68%	1,579	28.04%	635	11.28%
1920	3,752	66.25%	1,719	30.35%	192	3.39%
1916	2,902	50.72%	2,488	43.48%	332	5.80%
1912	715	27.43%	986	37.82%	906	34.75%
1908	1,183	55.99%	773	36.58%	157	7.43%
1904	1,107	62.51%	442	24.96%	222	12.54%

Along with Oregon State University, agriculture, lumber, wood products, and some printing technology research and development form the economic base of the county. A substantial portion of the nation's research in forestry, agriculture, engineering, education and the sciences takes place at OSU.

• National Register of Historic Places listings in Benton County, Oregon

• David D. Fagan, History of Benton County, Oregon: Including... a Full Political History, ...Incidents of Pioneer Life, and Biographical Sketches of Early and Prominent Citizens... Portland, OR: A.G. Walling, Printer, 1885.
• H.O. Lang (ed.), History of the Willamette Valley: Being a Description of the Valley and its Resources, with an Account of its Discovery and Settlement by White Men, and its Subsequent History; Together with Personal Reminiscences of its Early Pioneers. Portland: Himes and Lang, 1885.
• Benton County, Oregon, Illustrated: Published under Direction of the Benton County Citizens' League. n.c.: Benton County Citizens' League, 1904. —Copies in collections at OSU and UO libraries.
• Portrait and Biographical Record of the Willamette Valley, Oregon, Containing Original Sketches of Many Well Known Citizens of the Past and Present. Chicago: Chapman Publishing Co., 1903.
• Turnbull, George S. (1939). "Benton County" . History of Oregon Newspapers . Binfords & Mort.

• Benton County Government website
• Food Insecurity in Rural Benton County

44°29′25″N 123°25′57″W / 44.49028°N 123.43250°W / 44.49028; -123.43250