Whitman County is a county located in the U.S. state of Washington. As of the 2020 census, the population was 47,973. The county seat is Colfax, and its largest city is Pullman.

The county was formed from Stevens County in 1871. It is named after Marcus Whitman, a Presbyterian missionary who, with his wife Narcissa, was killed in 1847 by members of the Cayuse tribe.

Whitman County comprises the Pullman, Washington Metropolitan Statistical Area.

The area delineated by the future Washington state boundary began to be colonized at the start of the nineteenth century, both by Americans and Canadians. However, the majority of Canadian 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 dual control of this area by US and Canadian government officials. During this period, the future Washington Territory was divided into two administrative zones: Clark County and Lewis County (made official in 1845).

The dual-control concept was unwieldy and led to continual argument, and occasional conflict. The status of the Washington area was settled in 1846, when the Oregon Treaty ceded the land south of North latitude 49 degrees to American control.

In 1854, Skamania County was split from the original Clark County. Also in 1854, Walla Walla County was split from the new Skamania County. In 1863, Stevens County was split from Walla Walla County, and in 1871, a portion of Stevens County was set off to form Whitman County. The 1871 shape of Whitman County was considerably larger than its present boundary, as Adams, Franklin, and Lincoln counties were sectioned off from Whitman County in 1883. After that, Whitman County retained its shape, including through the period after Washington became the 42nd state of the Union in 1889.

According to the United States Census Bureau, the county has a total area of 2,178 square miles (5,640 km), of which 2,159 square miles (5,590 km) is land and 19 square miles (49 km) (0.9%) is water. Whitman County is part of the Palouse, a wide and rolling prairie-like region of the middle Columbia basin.

• Snake River
• Palouse River
  • Latah Creek
  • Union Flat Creek
  • Rock Creek
  • Pine Creek

• Lake Herbert G. West, formed from Lower Monumental Dam
• Lake Bryan, named for Dr. Enoch A. Bryan, behind the Little Goose Dam
• Lower Granite Lake, behind the Lower Granite Dam
• Rock Lake

• Tekoa Mountain (elevation: 4009')
• Kamiak Butte (elevation: 3641')
• Steptoe Butte (elevation: 3612')
• Bald Butte (elevation: 3369)

• Steptoe Butte State Park
• Kamiak Butte County Park
• Palouse Falls State Park
• Central Ferry State Park
• Boyer Park and Marina
• Wawawai County Park

• Pullman–Moscow Regional Airport: Airport with GA operations and a few airline flights with Alaska Airlines
• Port of Whitman Business Air Center Airport: Small GA Airport in Colfax

Historical population

Census	Pop.	Note	%±
1880	7,014		—
1890	19,109		172.4%
1900	25,360		32.7%
1910	33,280		31.2%
1920	31,323		−5.9%
1930	28,014		−10.6%
1940	27,221		−2.8%
1950	32,469		19.3%
1960	31,263		−3.7%
1970	37,900		21.2%
1980	40,103		5.8%
1990	38,775		−3.3%
2000	40,740		5.1%
2010	44,776		9.9%
2020	47,973		7.1%
2023 (est.)	48,012		0.1%
U.S. Decennial Census 1790–1960 1900–1990 1990–2000 2010–2020

As of the 2010 census, there were 44,776 people, 17,468 households, and 8,130 families living in the county. The population density was 20.7 people per square mile (8.0 people/km). There were 19,323 housing units at an average density of 8.9 units per square mile (3.4 units/km). The racial makeup of the county was 84.6% white, 7.8% Asian, 1.7% black or African American, 0.7% American Indian, 0.2% Pacific islander, 1.4% from other races, and 3.6% from two or more races. Those of Hispanic or Latino origin made up 4.6% of the population. In terms of ancestry, 29.4% were German, 14.5% were English, 13.4% were Irish, 7.1% were Norwegian, and 4.1% were American.

Of the 17,468 households, 20.8% had children under the age of 18 living with them, 38.4% were married couples living together, 5.4% had a female householder with no husband present, 53.5% were non-families, and 32.7% of all households were made up of individuals. The average household size was 2.22 and the average family size was 2.86. The median age was 24.4 years.

The median income for a household in the county was $36,368 and the median income for a family was $61,598. Males had a median income of $46,663 versus $34,496 for females. The per capita income for the county was $19,506. About 10.7% of families and 27.6% of the population were below the poverty line, including 13.3% of those under age 18 and 5.7% of those age 65 or over.

As of the 2000 census, there were 40,740 people, 15,257 households, and 8,055 families living in the county. The population density was 19 people per square mile (7.3 people/km). There were 16,676 housing units at an average density of 8 units per square mile (3.1 units/km). The racial makeup of the county was 88.07% White, 1.53% Black or African American, 0.73% Native American, 5.55% Asian, 0.27% Pacific Islander, 1.22% from other races, and 2.63% from two or more races. 2.99% of the population were Hispanic or Latino of any race. 21.9% were of German, 9.8% English, 8.6% Irish, 8.3% United States or American and 6.6% Norwegian ancestry.

There were 15,257 households, out of which 24.60% had children under the age of 18 living with them, 44.20% were married couples living together, 6.20% had a female householder with no husband present, and 47.20% were non-families. 29.40% of all households were made up of individuals, and 7.10% had someone living alone who was 65 years of age or older. The average household size was 2.31 and the average family size was 2.91.

In the county, the population was spread out, with 18.10% under the age of 18, 32.60% from 18 to 24, 24.00% from 25 to 44, 16.00% from 45 to 64, and 9.20% who were 65 years of age or older. The median age was 25 years. For every 100 females there were 102.50 males. For every 100 females age 18 and over, there were 101.90 males.

The median income for a household in the county was $28,584, and the median income for a family was $44,830. Males had a median income of $33,381 versus $27,046 for females. The per capita income for the county was $15,298. About 11.00% of families and 25.60% of the population were below the poverty line, including 16.50% of those under age 18 and 5.50% of those age 65 or over.

Despite the county historically voting for Republicans, Whitman County has a reputation as being far more socially liberal than other counties in Eastern Washington due to the presence of Washington State University in Pullman. It is part of Washington's 5th congressional district and is represented by Republican Cathy McMorris Rodgers. Quite conservative, rural Whitman was one of only three counties in the state to be won by Barry Goldwater in 1964. Since that election, the county has been won by the winning candidate in all but three presidential elections, 1976, 2012, and 2016. Richard Nixon, Ronald Reagan, Bill Clinton, and George W. Bush each won the county twice.

In 2008, Barack Obama received 51.57% of the Whitman County vote. In 2012, he received 46.9% of the vote, with Mitt Romney winning with a 49.7% plurality. Whitman was the only county in eastern Washington to approve same-sex marriage via Referendum 74. It was the only county to vote in favor of Referendum 74 while voting for the Republican candidate for president. Whitman County voters also approved marijuana legalization via Initiative 502.

By 2016, the county was considered Democratic in regard to federal elections. Hillary Clinton won the county in 2016 and also voted for Patty Murray in 2016. However, Republican Bill Bryant won this county over incumbent Democrat Jay Inslee by a percentage point in the concurrent gubernatorial election. In the 2020 elections, the majority of the county voted for Democrat Joe Biden for president and re-elected Inslee for governor. Both received majority of the county vote with Inslee becoming the first Democratic gubernatorial candidate to win a county in Eastern Washington since Gary Locke in 2000. However, the county still votes Republican in congressional elections.

In 2020, 52.9% of residents voted for Biden while 42.9% voted for Trump, a 10% margin for Biden.

United States presidential election results for Whitman County, Washington

Year	Republican		Democratic		Third party(ies)
	No.	%	No.	%	No.	%
2020	9,067	42.92%	11,184	52.94%	875	4.14%
2016	7,403	41.06%	8,146	45.19%	2,479	13.75%
2012	8,507	49.26%	8,037	46.54%	726	4.20%
2008	8,104	46.07%	9,070	51.57%	415	2.36%
2004	9,397	52.17%	8,287	46.01%	328	1.82%
2000	9,003	55.45%	6,509	40.09%	725	4.47%
1996	6,734	42.37%	7,262	45.69%	1,899	11.95%
1992	6,428	36.78%	7,637	43.69%	3,413	19.53%
1988	7,680	50.09%	7,403	48.28%	250	1.63%
1984	10,021	59.48%	6,621	39.30%	207	1.23%
1980	8,636	50.73%	5,726	33.63%	2,662	15.64%
1976	8,168	54.21%	6,197	41.13%	703	4.67%
1972	9,548	58.70%	6,248	38.41%	470	2.89%
1968	7,810	56.64%	5,218	37.84%	761	5.52%
1964	6,765	49.97%	6,760	49.93%	13	0.10%
1960	8,069	59.58%	5,458	40.30%	17	0.13%
1956	8,572	63.81%	4,854	36.13%	8	0.06%
1952	8,905	65.67%	4,611	34.00%	44	0.32%
1948	6,411	50.32%	6,015	47.21%	314	2.46%
1944	6,000	52.22%	5,449	47.42%	41	0.36%
1940	6,356	49.66%	6,351	49.62%	92	0.72%
1936	3,955	33.03%	7,753	64.75%	265	2.21%
1932	4,727	42.93%	5,945	53.99%	339	3.08%
1928	7,065	69.94%	2,969	29.39%	67	0.66%
1924	4,960	52.12%	1,745	18.34%	2,811	29.54%
1920	6,344	64.68%	2,806	28.61%	659	6.72%
1916	4,933	43.84%	5,888	52.33%	430	3.82%
1912	1,989	20.00%	3,621	36.42%	4,333	43.58%
1908	3,376	52.60%	2,386	37.18%	656	10.22%
1904	4,090	66.48%	1,519	24.69%	543	8.83%
1900	2,366	42.52%	2,826	50.78%	373	6.70%
1896	1,592	29.66%	3,690	68.75%	85	1.58%
1892	2,131	37.33%	2,061	36.10%	1,517	26.57%

Whitman County has highly productive agriculture. According to Heart of Washington, Whitman County produces more barley, wheat, dry peas, and lentils than any other county in the United States.

The county is also home to Schweitzer Engineering Laboratories in Pullman.

Pullman is home to Washington State University, the state's land-grant university.

• Colfax (county seat)
• Palouse
• Pullman
• Tekoa

• Steptoe

• Elberton

• 
  Colfax
• 
  Farmington
• 
  Palouse
• 
  Pullman
• 
  Steptoe

• 
  A farm in Whitman County
• 
  Lower Granite Dam and Boyer Park and Marina on the Snake River
• 
  Palouse Falls
• 
  Steptoe Butte
• 
  Wawawai County Park

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

• Whitman County – official website
• Whitman County Genealogical Society
• Whitman County Historical Society
• Whitman County Library with branches in 14 communities throughout Whitman County.
• Whitman County Heritage A collection of historic materials from the Whitman County Library and local partners.
• Whitman County @ State of Washington Office of Financial Management
• Port of Whitman County and Green IT Alliance (GITA)

46°53′N 117°31′W / 46.89°N 117.52°W / 46.89; -117.52