Washington Counties by Population (2025)

There are 39 counties in Washington.

Washington’s most populous county is King County, home to Seattle, with a population of 2,188,649. This represents a 12.97% population growth since the 2010 census.

Washington is followed by:

• Pierce County: 876,764
• Snohomish County: 801,633
• Spokane County: 506,152

These are the only counties in Washington with a population of more than 500,000. All four counties have posted significant growth since the census ranging from 7% to almost 13%.

Washington Counties with Fewest Residents

The least populous county in Washington is Garfield County with a population of 2,210. This represents a population decline of -2.26% since the last census.

Other sparsely populated counties in Washington include:

• Columbia County: 4,047
• Wahkiakum County: 4,264
• Ferry County: 7,594

These are the only counties in Washington with a population under 10,000. Three of these counties reported a population decline since 2010. Wahkiakum County had population growth of 7.05% since the last census.

Washington Counties with Rapid Growth

Franklin County has boasted the highest population growth rate in Washington since the last census, growing 16.48% to 92,125.

Four other counties have experienced population growth above 12%:

• King County: Growth rate of 12.97%
• Kittitas County: Growth rate of 12.74%
• Benton County: Growth rate of 12.30%
• Snohomish County: Growth rate of 12.05%

The county with the largest negative growth is Garfield County, with a decline of -2.26%.