King County, Washington

King County at a glance.

King County had an estimated 2,340,211 residents in July 2024, the most populous of Washington's 39 counties, up 3.1% since the 2020 census. Of those, 1,898,790 are 18 or older, the voting-age population, and 14.6% are 65 or older. Its 1,445,755 active registered voters equal about 76.1% of that voting-age population.

It covers 2,116 square miles of land (1,106 people per square mile), and 10.4% of residents live outside any incorporated city or town. The largest cities and towns are Seattle (780,995), Bellevue (154,377), Kent (136,588), Renton (105,543) and Federal Way (100,252). The American Community Survey (2020-2024) puts it at a median age of 37.4, a median household income of $124,746, 56.7% of adults 25 and older holding a bachelor's degree or higher and 55.4% of occupied homes owned by the people living in them.

In 2024, 1,122,881 votes were cast for president, about 59.1% of the voting-age population; the Democratic ticket took 74.1% and the Republican ticket 22.5%. The two-party margin moved from D+42.1 in 2008 to D+51.6 in 2024.

Population (2024 estimate)

2,340,211

Population (2020 census base)

2,269,666

Voting-age population (18+)

1,898,790

Active voters per 100 adults

76.1

Residents 65 and older

14.6%

People per square mile

1,106

Living outside incorporated places

10.4%

Land area

2,116 sq mi

Median age

37.4

Median household income

$124,746

Adults 25+ with a bachelor's degree

56.7%

Owner-occupied homes

55.4%

Largest cities and towns

1. Seattle 780,995
2. Bellevue 154,377
3. Kent 136,588
4. Renton 105,543
5. Federal Way 100,252

Presidential vote, 2008–2024

Sources: U.S. Census Bureau Vintage 2024 population estimates and 2024 Gazetteer; American Community Survey 2020–2024 5-year estimates; certified county presidential returns. Growth, density and turnout are simple arithmetic on those figures.