King County, Washington

King County is a county in Washington, United States, anchored by Seattle on Puget Sound about
25 miles north of Tacoma. It had a population of 2,269,675 at the 2020 census, an estimated
2,344,939 by 2024, and covers 2,307 square miles (5,980 km2) centred near 47°28′N 121°50′W.

Seattle is the county seat and by far the largest city; its postal code is 98104. The county
holds 35 incorporated cities and 4 incorporated towns, plus a large unincorporated area with
hundreds of named neighborhoods and rural communities, and it runs on Pacific Time. Its FIPS code
is 53033.

Towns & Villages in King County

King County has 39 incorporated cities and towns on record, ranging from Seattle’s
737,015 residents to Skykomish’s 161, listed largest first below. “City ·
seat” marks Seattle; Beaux Arts Village, Hunts Point, Skykomish and Yarrow Point are
incorporated as towns rather than cities under Washington law, a smaller legal category with the
same self-government powers.

Four places straddle King County’s border with a neighbor. Bothell’s 48,161 is
citywide — most of the city sits in King County, but its northern edge extends into
Snohomish County. Auburn reaches south into Pierce County the same way. Pacific spans the
King–Pierce line along the Green River, and Milton runs the opposite direction: it is
chiefly a Pierce County city, with only a small eastern slice of its 8,697 residents inside King
County.

Beyond the incorporated list, King County has dozens of unincorporated communities the Census
Bureau recognizes as census-designated places (CDPs). The largest are set out below; smaller
crossroads and rural settlements exist well beyond this list. Seattle’s own internal
neighborhoods — Ballard, Fremont, Capitol Hill, Georgetown and the rest — are
districts of the city itself, not separate places, despite older directories sometimes listing
them as standalone towns.

ZIP Codes

King County uses well over 70 ZIP codes: one or more per incorporated city, plus a further set
for unincorporated areas and Seattle’s own dozens of postal zones. Seattle alone runs from
98101 in the downtown core through the 98103–98199 range covering its neighborhoods;
Bellevue’s codes run 98004–98008, Kent’s 98030–98032, and
Redmond’s 98052–98053. Most other incorporated cities carry a single core code
— Kirkland 98033, Renton 98057, Federal Way 98003, Auburn 98001, Issaquah 98027, Sammamish
98074, Kenmore 98028, Woodinville 98072, Snoqualmie 98065, Enumclaw 98022, Carnation 98014,
Duvall 98019, North Bend 98045, Black Diamond 98010 and Skykomish 98288 among them. The tiny
Eastside towns of Clyde Hill, Yarrow Point, Hunts Point and Beaux Arts Village all share
Bellevue’s 98004 code, since none is large enough on its own to support a separate post
office.

Geography

King County straddles the Puget Sound lowland and the Cascade Range, running from saltwater
shoreline in the west to alpine peaks in the east. Of its 2,307 square miles, 2,116 square miles
(5,480 km2) are land and 191 square miles (490 km2) are water, about 8.3 percent — Lake
Washington and Lake Sammamish account for most of the freshwater, while Puget Sound forms the
county’s western edge. Mount Daniel, at 7,959 feet (2,426 meters), is the county’s
highest point, and the Snoqualmie and Green–Duwamish rivers are its principal waterways,
with Snoqualmie Falls a well-known landmark on the former.

Snohomish County lies to the north, Pierce County to the south, Kitsap County across Puget
Sound to the west, and Chelan County and Kittitas County over the Cascade crest to the east.
Snohomish County,
Pierce County,
Kitsap County,
Chelan County and
Kittitas County all border King
County directly.

Demographics

King County had a population of 2,269,675 at the 2020 census, up from 1,931,249 in 2010, and
the latest estimate puts the county near 2,344,939 residents by 2024. Seattle and Bellevue are by
far the two largest communities, together holding well over a third of the county’s
population. Median household income runs $124,746, well above Washington’s statewide
figure of $94,600. Population density works out to roughly 1,073 people per square mile of land,
among the highest in the Pacific Northwest outside a handful of dense West Coast metros.

Economy & Local Life

Professional, scientific and technical services is the county’s largest employment
sector, with about 227,948 workers, followed by health care and social assistance at 150,442 and
retail trade at 148,767. Boeing’s commercial-airplane operations run out of Renton, where
the 737 has been built since the 1960s. Microsoft is headquartered in Redmond, and Amazon and
Expedia anchor Seattle’s downtown and South Lake Union districts. Costco Wholesale is
headquartered in Issaquah. The county’s biggest annual event is Seattle Seafair each
August, a weeks-long festival built around hydroplane races on Lake Washington and a Blue Angels
air show.

History

The Washington territorial legislature created King County on December 22, 1852, naming it
for Vice President-elect William Rufus King. In 2005 the county council formally re-designated
the name’s honoree as civil-rights leader Martin Luther King Jr., without changing the
county’s name itself. The Duwamish and other Coast Salish peoples had lived around Puget
Sound for thousands of years before the Denny Party landed at Alki Point in 1851 and founded what
became Seattle. Coal mining drove the early economy around Newcastle and Black Diamond in the
late 1800s, and Seattle’s Klondike Gold Rush-era boom, beginning in 1897, turned the city
into the main supply port for prospectors headed to Alaska and the Yukon.

Getting There

Interstate 5 runs the length of the county along Puget Sound, Interstate 90 crosses it
east–west over Snoqualmie Pass, and Interstate 405 loops around Lake Washington’s
east side. State Route 520 crosses Lake Washington between Seattle and the Eastside, and State
Route 99 carries heavy commuter traffic through Seattle itself.

• Seattle — central to the county
• Tacoma — about 25 miles south
• Everett — about 25 miles north
• North Bend — about 30 miles east

Seattle–Tacoma International Airport, in the city of SeaTac, is the region’s main
commercial airport. Amtrak’s King Street Station in downtown Seattle serves the Coast
Starlight, Empire Builder and Cascades routes, and Washington State Ferries link West Seattle,
Vashon Island and Fauntleroy to terminals across Puget Sound.

Frequently Asked Questions

Where is King County located?
It sits on central Puget Sound in western Washington, bordered by Snohomish County to the north,
Pierce County to the south, Kitsap County across the Sound to the west, and Chelan and Kittitas
counties over the Cascades to the east.

What is the population of King County?
2,269,675 at the 2020 census, with an estimate near 2,344,939 by 2024.

How big is King County?
2,307 square miles (5,980 km2) in total, of which 2,116 square miles are land.

What is the county seat of King County?
Seattle, founded in 1851, is the county seat and by far the largest city.

How many towns and cities are in King County?
35 incorporated cities and 4 incorporated towns, plus dozens of unincorporated communities such
as Vashon and Fairwood.

What ZIP codes does King County use?
Well over 70, from Seattle’s 98101–98199 range to single core codes like
Bellevue’s 98004 and Kirkland’s 98033.

What is King County known for?
Boeing’s Renton plant, Microsoft’s Redmond headquarters, Amazon and Costco, and
being re-designated in 2005 to honor Martin Luther King Jr.

More counties in this state: Towns and villages in Washington.