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Basic Information

2010 Census Population: 6,724,540 (13th)
Land Area: 66,455.5 square miles (20th)
Density: 101.2 persons per square mile (25th)
Capital: Olympia
Became a State: November 11, 1889 (42nd)
Bordering States: Idaho, Oregon
International Border: Canada
Abbreviation: WA
ANSI Code: 53

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The United States acquired the area of Washington through a treaty with Great Britain in 1846. Washington Territory was organized from part of Oregon Territory on March 2, 1853; it included all of present-day Washington, northern Idaho, and northwestern Montana. In 1859, when Oregon was admitted as a state, the remainder of Oregon Territory the rest of Idaho, additional area of Montana, and part of Wyoming was added to Washington Territory. Washington Territory assumed generally the same boundary as the present state when Idaho Territory was organized in 1863. Washington was admitted to the Union on November 11, 1889, as the 42nd state.

Although the territory had not yet been legally established, census data for Washington are available beginning with the 1850 census. The 1850 and 1860 populations are for the entire territory as legally established in 1859, when it included all of Idaho and part of Montana and Wyoming. The population of the entire legally established Oregon Territory (of which the area of Washington was a part) in 1850 was 13,294.

Data for the legally established state of Washington are available beginning with the 1890 census.


Washington has 27 federally recognized American Indian reservations, 15 with off-reservation trust land.  There is also one tribal designated statistical area (TDSA).

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About the Geographic Areas


Washington has 12 metropolitan statistical areas, 9 micropolitan statistical areas, 2 metropolitan divisions, and 1 combined statistical area.


There are 39 counties in Washington.  All counties are functioning governmental units, each governed by a board of county commissioners except for Clallam, King, Pierce, Snohomish, and Whatcom Counties which are each governed by a county council.  Six counties, Clallam, King, Pierce, San Juan, Snohomish, and Whatcom, have Home Rule Charters, which among other things, give the counties broad planning powers.


There are 242 county subdivisions in Washington. They are all census county divisions (CCDs), which are delineated for statistical purposes, have no legal function, and are not governmental units.  CCDs were first established in Washington for the 1950 census.  Prior to 1950, the minor civil divisions included election precincts, townships and/or land survey townships, and American Indian reservations.


Washington has 628 places, 281 incorporated places and 347 are census designated places (CDPs).  The incorporated places consist of 208 cities and 73 towns.  A minimum population of 3,000 is required for incorporation if the new entity is within 5 air miles of the boundary of a city with a population of 15,000 or more. 


Washington has 1,458 census tracts, 4,783 block groups, and 195,574 census blocks.


For the 111th Congress (January 2009-January 2011), Washington had nine congressional districts.  For the 113th Congress (January 2013-January 2015), Washington has ten congressional districts as a result of reapportionment based on the 2010 Census.


Washington has 295 unified school districts.


There are 49 state senate districts and 49 state house districts in Washington.


Washington has 81 urban areas; 14 urbanized areas and 67 urban clusters.


There are 598 ZIP Code tabulation areas (ZCTAs) in Washington.

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Centers of Population

Year North Latitude West Longitude
20106 47° 19′ 51″ 121° 37′ 12″
20006 47° 20′ 30″ 121° 37′ 28″
19905 47° 21′ 09″ 121° 36′ 46″
19804 47° 20′ 11″ 121° 31′ 57″
19703 47° 21′ 10″ 121° 31′ 57″
19603 47° 21′ 11″ 121° 24′ 04″
19503 47° 20′ 26″ 121° 23′ 04″
19402 47° 19′ 48″ 121° 09′ 34″
19302 47° 20′ 36″ 121° 09′ 12″
19201 47° 24′ 05″ 121° 14′ 24″
19101 47° 23′ 06″ 121° 04′ 16″
19001 47° 19′ 50″ 120° 46′ 35″
18901 47° 15′ 44″ 120° 52′ 30″
18801 47° 05′ 32″ 120° 36′ 29″

1  Source:  U.S. Department of Commerce, Bureau of the Census, Fourteenth Census of the United States, 1923
2  Source:  U.S. Census Bureau, recomputation for historical county level data which relied upon aggregate county level population data with an estimated county centroid resulting in a possible error of up to one mile.
3  Source:  U.S. Department of Commerce, Bureau of the Census, Centers of Population for States and Counties, 1974
4  Source:  U.S. Census Bureau, Geography Division, recomputation from archived national block group/enumeration area data resulting in a possible error of up to 1,000 feet.
5  Source:  U.S. Census Bureau, Geography Division, recomputation from archived national block group data resulting in a possible error of up to 1,000 feet.
6  Source:  U.S. Census Bureau, computation from national block-level data

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Most Populous, Largest, and Dense Areas

Population Land Area
(square miles)
Population Density
(Persons per square mile)

Name Population Name Area Name Density
County King County 1,931,249 Okanogan County 5,267.98 King County 912.9

 - Inc Place Seattle city 608,660 Seattle city 83.94 Seattle city 7,250.9
 - CDP South Hill CDP 52,431 Vashon CDP 36.92 White Center CDP 6,020.8

List of Entities

See the Gazetteer Files for a list of geographic entities. See the Metropolitan and Micropolitan Statistical Areas page for a list of metropolitan and micropolitan statistical areas and related statistical areas.

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