Garfield County is a county located in the U.S. state of Washington. As of the 2020 census, the population was 2,286, making it the least populous county in Washington; with about 3.2 inhabitants per square mile (1.2/km), it is also the least densely populated county in Washington. The county seat and only city is Pomeroy.

The area delineated by the future Washington state boundary began to be colonized at the start of the nineteenth century, both by Americans and British. However, the majority of British exploration and interest in the land was due to the fur trade, whereas American settlers were principally seeking land for agriculture and cattle raising. The Treaty of 1818 provided for the creation of a British and American condominium over the region. During this period, the future Washington Territory was divided into two administrative zones, Clark County and Lewis County, officially in 1845. However, the condominium arrangement was unwieldy, leading to continuous disputes and occasional conflict; it was abolished by an 1846 treaty that established a boundary between British and American possessions that survives as today's Canada–United States border.

In 1854, Skamania County was split from the original Clark County and Walla Walla County was split from the new Skamania County. In 1875, Columbia County was split from Walla Walla County, and on November 29, 1881, a portion of Columbia County was set off to form Garfield County. The original Garfield County was reduced in size in 1883 when its southeastern area was partitioned off to form Asotin County. It was named for the late U.S. President James A. Garfield, who had been assassinated a few weeks prior.

According to the United States Census Bureau, the county has a total area of 718 square miles (1,860 km), of which 711 square miles (1,840 km) is land and 7.5 square miles (19 km) (1.0%) is water. It is part of the Palouse, a wide and rolling prairie-like region of the middle Columbia basin.

• Alpowa Summit
• Snake River

• U.S. Route 12
• State Route 127

• Whitman County - north
• Asotin County - east
• Wallowa County, Oregon - south
• Columbia County - west

• Umatilla National Forest (part)

Historical population

Census	Pop.	Note	%±
1890	3,897		—
1900	3,918		0.5%
1910	4,199		7.2%
1920	3,875		−7.7%
1930	3,662		−5.5%
1940	3,383		−7.6%
1950	3,204		−5.3%
1960	2,976		−7.1%
1970	2,911		−2.2%
1980	2,468		−15.2%
1990	2,248		−8.9%
2000	2,397		6.6%
2010	2,266		−5.5%
2020	2,286		0.9%
2023 (est.)	2,363		3.4%
U.S. Decennial Census 1790–1960 1900–1990 1990–2000 2010–2020

As of the 2010 census, there were 2,266 people, 989 households, and 650 families living in the county. The population density was 3.2 inhabitants per square mile (1.2/km). There were 1,233 housing units at an average density of 1.7 units per square mile (0.66 units/km). The racial makeup of the county was 93.8% white, 1.7% Asian, 0.3% American Indian, 2.3% from other races, and 1.9% from two or more races. Those of Hispanic or Latino origin made up 4.0% of the population. In terms of ancestry, 27.2% were German, 22.4% were English, 19.9% were Irish, 7.9% were Dutch, 5.5% were Swedish, and 3.4% were American.

Of the 989 households, 25.1% had children under the age of 18 living with them, 55.6% were married couples living together, 6.1% had a female householder with no husband present, 34.3% were non-families, and 30.2% of all households were made up of individuals. The average household size was 2.25 and the average family size was 2.79. The median age was 49.0 years.

The median income for a household in the county was $42,469 and the median income for a family was $55,769. Males had a median income of $38,897 versus $30,650 for females. The per capita income for the county was $22,825. About 14.1% of families and 15.7% of the population were below the poverty line, including 22.1% of those under age 18 and 6.6% of those age 65 or over.

As of the 2000 census, there were 2,397 people, 987 households, and 670 families living in the county. The population density was 3 people per square mile (1.2 people/km). There were 1,288 housing units at an average density of 2 units per square mile (0.77 units/km). The racial makeup of the county was 96.45% White, 0.38% Native American, 0.67% Asian, 0.04% Pacific Islander, 1.38% from other races, and 1.08% from two or more races. 1.96% of the population were Hispanic or Latino of any race. 28.8% were of German, 17.9% United States or American, 10.6% English and 9.5% Irish ancestry. 99.2% spoke English as their first language.

There were 987 households, out of which 28.80% had children under the age of 18 living with them, 57.00% were married couples living together, 6.70% had a female householder with no husband present, and 32.10% were non-families. 28.30% of all households were made up of individuals, and 14.40% had someone living alone who was 65 years of age or older. The average household size was 2.39 and the average family size was 2.93.

In the county, the population was spread out, with 25.90% under the age of 18, 5.40% from 18 to 24, 21.90% from 25 to 44, 25.90% from 45 to 64, and 20.90% who were 65 years of age or older. The median age was 43 years. For every 100 females there were 97.90 males. For every 100 females age 18 and over, there were 93.80 males.

The median income for a household in the county was $33,398, and the median income for a family was $41,645. Males had a median income of $33,313 versus $22,132 for females. The per capita income for the county was $16,992. About 12.00% of families and 14.20% of the population were below the poverty line, including 17.10% of those under age 18 and 10.20% of those age 65 or over.

• Pomeroy (county seat)

• Dodge
• Gould City
• Mayview
• Mentor
• Pataha
• Peola

• Unfried

Part of the 1996 film Black Sheep takes place in Garfield County, but was not filmed there.

Garfield County has consistently voted for Republican candidates in presidential elections throughout its history. In only four elections since 1896 have more voters chosen the Democratic candidate, the most recent being the 1964 election. In 1912 the plurality of votes went instead to the Progressive Party candidate, former Republican president Theodore Roosevelt.

United States presidential election results for Garfield County, Washington

Year	Republican		Democratic		Third party(ies)
	No.	%	No.	%	No.	%
2024	973	71.97%	330	24.41%	49	3.62%
2020	1,069	71.79%	366	24.58%	54	3.63%
2016	851	67.22%	279	22.04%	136	10.74%
2012	913	71.27%	336	26.23%	32	2.50%
2008	968	70.50%	385	28.04%	20	1.46%
2004	935	70.83%	365	27.65%	20	1.52%
2000	982	73.89%	300	22.57%	47	3.54%
1996	623	49.64%	497	39.60%	135	10.76%
1992	620	46.93%	473	35.81%	228	17.26%
1988	714	54.13%	593	44.96%	12	0.91%
1984	913	63.94%	493	34.52%	22	1.54%
1980	875	57.60%	509	33.51%	135	8.89%
1976	892	57.18%	616	39.49%	52	3.33%
1972	1,004	65.45%	481	31.36%	49	3.19%
1968	841	53.03%	602	37.96%	143	9.02%
1964	751	49.02%	781	50.98%	0	0.00%
1960	914	56.88%	690	42.94%	3	0.19%
1956	966	60.15%	639	39.79%	1	0.06%
1952	1,157	66.76%	559	32.26%	17	0.98%
1948	749	48.92%	747	48.79%	35	2.29%
1944	925	57.38%	677	42.00%	10	0.62%
1940	1,003	58.08%	714	41.34%	10	0.58%
1936	652	38.83%	983	58.55%	44	2.62%
1932	669	44.42%	818	54.32%	19	1.26%
1928	1,004	70.60%	412	28.97%	6	0.42%
1924	875	65.25%	324	24.16%	142	10.59%
1920	869	66.03%	370	28.12%	77	5.85%
1916	845	52.26%	728	45.02%	44	2.72%
1912	345	22.16%	426	27.36%	786	50.48%
1908	556	58.53%	333	35.05%	61	6.42%
1904	777	70.32%	267	24.16%	61	5.52%
1900	528	52.59%	437	43.53%	39	3.88%
1896	378	43.20%	482	55.09%	15	1.71%
1892	351	36.26%	288	29.75%	329	33.99%

• National Register of Historic Places listings in Garfield County, Washington

• Frank T. Gilbert, Historic Sketches: Walla Walla, Columbia and Garfield Counties, Washington Territory. Portland, OR: A.G. Walling Printing House, 1882.
• W.D. Lyman, Lyman's History of Old Walla Walla County, Embracing Walla Walla, Columbia, Garfield and Asotin Counties. In Two Volumes. Chicago: S.J. Clarke Publishing Co., 1918. Volume 1 | Volume 2
• Frederic Ambrose Shaver, An Illustrated History of Southeastern Washington, Including Walla Walla, Columbia, Garfield and Asotin Counties, Washington. Spokane, WA: Western Historical Publishing Co., 1906.

46°26′N 117°32′W / 46.43°N 117.53°W / 46.43; -117.53