Island County is a county located in the U.S. state of Washington. As of the 2020 census, its population was 86,857. Its county seat is Coupeville, while its largest city is Oak Harbor.

The county's name reflects the fact that it is composed entirely of islands. It contains two large islands, Whidbey and Camano, and seven smaller islands (Baby, Ben Ure, Deception, Kalamut, Minor, Smith, and Strawberry). Island County was created out of Thurston County on December 22, 1852, by the legislature of Oregon Territory, and is the eighth-oldest county in Washington. It originally encompassed what are now Snohomish, Skagit, Whatcom, and San Juan Counties.

Island County comprises the Oak Harbor, Washington Micropolitan Statistical Area, which is also included in the Seattle–Tacoma, WA Combined Statistical Area.

According to the United States Census Bureau, the county has a total area of 517 square miles (1,340 km), of which 208 square miles (540 km) is land and 309 square miles (800 km) (60%) is water. It is the second smallest county in Washington by land area after San Juan, and second smallest by total area after Wahkiakum.

• Puget Sound
• Strait of Juan de Fuca
• Whidbey Island
• Camano Island
• Saratoga Passage

• Pacific Northwest National Scenic Trail (part)
• Ebey's Landing National Historical Reserve

Historical population

Census	Pop.	Note	%±
1860	294		—
1870	626		112.9%
1880	1,087		73.6%
1890	1,787		64.4%
1900	1,870		4.6%
1910	4,704		151.6%
1920	5,489		16.7%
1930	5,369		−2.2%
1940	6,098		13.6%
1950	11,079		81.7%
1960	19,638		77.3%
1970	27,011		37.5%
1980	44,048		63.1%
1990	60,195		36.7%
2000	71,558		18.9%
2010	78,506		9.7%
2020	86,857		10.6%
2023 (est.)	86,267		−0.7%
U.S. Decennial Census 1790–1960 1900–1990 1990–2000 2010–2020

As of the 2020 census, there were 86,857 people, 35,917 households, and 24,229 families living in the county. The population density was 416.6 inhabitants per square mile (160.9/km). There were 41,922 housing units at an average density of 201.1 inhabitants per square mile (77.6/km). The racial makeup of the county was 78.2% White, 2.8% African American, 0.8% Native American, 4.6% Asian, 0.5% Pacific Islander, 2.7% from some other races and 10.4% from two or more races. Hispanic or Latino people of any race were 8.2% of the population. 17.0% of residents were under the age of 18, 4.5% were under 5 years of age, and 27.8% were 65 and older.

As of the 2010 census, there were 78,506 people, 32,746 households, and 22,156 families living in the county. The population density was 376.6 inhabitants per square mile (145.4/km). There were 40,234 housing units at an average density of 193.0 per square mile (74.5/km). The racial makeup of the county was 86.1% white, 4.4% Asian, 2.2% black or African American, 0.8% American Indian, 0.5% Pacific islander, 1.5% from other races, and 4.5% from two or more races. Those of Hispanic or Latino origin made up 5.5% of the population. The largest ancestry groups were:

Of the 32,746 households, 27.3% had children under the age of 18 living with them, 56.6% were married couples living together, 7.9% had a female householder with no husband present, 32.3% were non-families, and 25.9% of all households were made up of individuals. The average household size was 2.35 and the average family size was 2.81. The median age was 43.2 years.

The median income for a household in the county was $57,190 and the median income for a family was $68,106. Males had a median income of $46,801 versus $35,189 for females. The per capita income for the county was $29,079. About 5.7% of families and 8.0% of the population were below the poverty line, including 12.1% of those under age 18 and 4.0% of those age 65 or over.

The primary islands of Island County, Whidbey Island and Camano Island are served by a total of 3 Washington State Routes, those being SR 20 and SR 525 on Whidbey Island, and SR 532 on Camano Island. SR 20 enters Island County via the Port Townsend-Coupeville (Keystone) ferry route from the West, and departs via the Deception Pass Bridge in the North. SR 525 enters Island County from the East/South via the Mukilteo-Clinton ferry and terminates at an intersection with SR 20, South of Coupeville. SR 532 begins on Camano Island at Terry's Corner and departs Island County to the East via the Camano Gateway Bridge.

These islands are also served by a fare-free/pre-paid bus service called Island Transit.

The county government is led by a board of commissioners with three elected members that represent geographical regions of Island County.

Island County is divided politically between its north and south. While the north (Oak Harbor) is conservative – Donald Trump received almost 55 percent of the 2016 vote and carried most precincts – most southern and central precincts voted for Hillary Clinton.

The south-central area (Coupeville, Langley) voted over 50 percent for Clinton, just over 30 percent for Trump.

United States presidential election results for Island County, Washington

Year	Republican		Democratic		Third party(ies)
	No.	%	No.	%	No.	%
2024	20,967	39.98%	29,595	56.43%	1,887	3.60%
2020	22,746	42.18%	29,213	54.17%	1,966	3.65%
2016	18,465	41.71%	20,960	47.34%	4,848	10.95%
2012	19,605	46.27%	21,478	50.69%	1,289	3.04%
2008	19,426	46.07%	22,058	52.31%	680	1.61%
2004	19,754	51.20%	18,216	47.22%	610	1.58%
2000	16,408	49.72%	14,778	44.78%	1,818	5.51%
1996	12,387	43.52%	12,157	42.71%	3,920	13.77%
1992	9,526	35.06%	9,555	35.17%	8,087	29.77%
1988	12,552	58.78%	8,510	39.85%	291	1.36%
1984	13,548	65.72%	6,850	33.23%	218	1.06%
1980	10,926	58.87%	5,422	29.21%	2,211	11.91%
1976	7,804	55.33%	5,859	41.54%	441	3.13%
1972	7,495	68.12%	3,149	28.62%	359	3.26%
1968	4,077	50.96%	3,238	40.48%	685	8.56%
1964	3,044	43.49%	3,946	56.38%	9	0.13%
1960	3,596	59.01%	2,470	40.53%	28	0.46%
1956	3,196	61.20%	2,009	38.47%	17	0.33%
1952	2,901	61.68%	1,772	37.68%	30	0.64%
1948	1,805	49.05%	1,694	46.03%	181	4.92%
1944	1,487	46.66%	1,662	52.15%	38	1.19%
1940	1,371	44.85%	1,626	53.19%	60	1.96%
1936	921	32.74%	1,687	59.97%	205	7.29%
1932	803	30.17%	1,517	56.99%	342	12.85%
1928	1,487	71.25%	556	26.64%	44	2.11%
1924	832	46.25%	114	6.34%	853	47.42%
1920	883	51.19%	285	16.52%	557	32.29%
1916	804	43.58%	855	46.34%	186	10.08%
1912	332	21.11%	310	19.71%	931	59.19%
1908	450	58.21%	192	24.84%	131	16.95%
1904	424	71.99%	83	14.09%	82	13.92%
1900	263	62.62%	123	29.29%	34	8.10%
1896	206	50.86%	191	47.16%	8	1.98%
1892	161	40.66%	127	32.07%	108	27.27%

• Langley
• Oak Harbor

• Coupeville (county seat)

• Camano
• Clinton
• Freeland
• Whidbey Island Station, formerly listed as Ault Field

Juniper Beach, a wedding ceremony locale in past years, has given its name to the Juniper Beach Water District.

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

• Official website

48°09′N 122°35′W / 48.15°N 122.58°W / 48.15; -122.58