County facts · Population growth · October 23, 2026
Fastest Growing Counties in Washington State, 2020 to 2025
Washington's fastest growing counties by percent and by people added, April 2020 to July 2025 Census estimates, with each official parcel map.
Looking for the fastest growing counties in Washington? From the Census Bureau's April 1, 2020 estimates base to its July 1, 2025 estimate, Washington went from about 7,707,519 to 8,001,020 residents, a change of +293,501 (+3.8%). The fastest growing county by percentage was Wahkiakum County (+10.2%), while King County added the most people (+75,271, +3.3%).
Every row below links to the county's Platbookmapper page and straight to its official parcel viewer, handy if growth is why you are looking at land there.
Washington growth at a glance
- County: 39
- Statewide, April 2020 to July 2025: +293,501 residents (+3.8%); July 2024 to July 2025 alone: +73,062 (+0.9%)
- Grew: 37 of 39 · Lost residents: 2
- Fastest growing by percent: Wahkiakum County (+10.2%); most people added: King County (+75,271)
- Counties with more deaths than births over the period: 25 of 39
The 10 fastest growing Washington counties by percent
| # | County | Apr 2020 | Jul 2025 | Change | % change | Parcel viewer |
|---|---|---|---|---|---|---|
| 1 | Wahkiakum County | 4,420 | 4,873 | +453 | +10.2% | ArcGIS Experience Builder |
| 2 | Lincoln County | 10,878 | 11,982 | +1,104 | +10.1% | Washington Current Parcels layer in ArcGIS Map Viewer |
| 3 | Mason County | 65,721 | 71,165 | +5,444 | +8.3% | county web map |
| 4 | Douglas County | 42,935 | 46,473 | +3,538 | +8.2% | ArcGIS Experience Builder |
| 5 | Pend Oreille County | 13,402 | 14,457 | +1,055 | +7.9% | Washington Current Parcels layer in ArcGIS Map Viewer |
| 6 | Okanogan County | 42,097 | 45,230 | +3,133 | +7.4% | Washington Current Parcels layer in ArcGIS Map Viewer |
| 7 | Lewis County | 82,144 | 88,062 | +5,918 | +7.2% | county web map |
| 8 | Benton County | 206,863 | 221,722 | +14,859 | +7.2% | county web map |
| 9 | Klickitat County | 22,731 | 24,331 | +1,600 | +7.0% | Washington Current Parcels layer in ArcGIS Map Viewer |
| 10 | Stevens County | 46,445 | 49,668 | +3,223 | +6.9% | Washington Current Parcels layer in ArcGIS Map Viewer |
These 10 added about 40,327 people combined. The median county changed by +4.4%.
The 10 counties that added the most people
| # | County | People added | % change | Jul 2025 | Parcel viewer |
|---|---|---|---|---|---|
| 1 | King County | +75,271 | +3.3% | 2,344,939 | county web map |
| 2 | Snohomish County | +42,709 | +5.2% | 870,656 | ArcGIS Experience Builder |
| 3 | Clark County | +28,811 | +5.7% | 532,119 | county web map |
| 4 | Pierce County | +25,137 | +2.7% | 946,288 | county web map |
| 5 | Spokane County | +19,011 | +3.5% | 558,344 | county web map |
| 6 | Benton County | +14,859 | +7.2% | 221,722 | county web map |
| 7 | Whatcom County | +9,547 | +4.2% | 236,392 | ArcGIS Experience Builder |
| 8 | Thurston County | +9,471 | +3.2% | 304,261 | county web map |
| 9 | Kitsap County | +7,760 | +2.8% | 283,374 | county web map |
| 10 | Grant County | +6,592 | +6.6% | 105,727 | Washington Current Parcels layer in ArcGIS Map Viewer |
The top 10 account for about 81% of all the gains in the counties that grew.
Where the new residents came from
The Census Bureau splits each change into natural change (births minus deaths), net domestic migration (moves from other parts of the US) and net international migration. Totals for April 2020 to July 2025 in the five fastest growing counties:
| County | Births minus deaths | Net domestic moves | Net international moves | Total change |
|---|---|---|---|---|
| Wahkiakum County | −164 | +624 | +1 | +453 |
| Lincoln County | −158 | +1,260 | +10 | +1,104 |
| Mason County | −938 | +5,092 | +1,351 | +5,444 |
| Douglas County | +595 | +1,958 | +1,009 | +3,538 |
| Pend Oreille County | −511 | +1,579 | +10 | +1,055 |
In all 5, moves from elsewhere in the US were the biggest source of growth. The three parts do not add up exactly to the total because the Census Bureau also carries a small residual.
The last year alone: July 2024 to July 2025
- Columbia County: +2.3% (+95)
- Douglas County: +2.1% (+956)
- Mason County: +2.0% (+1,406)
- Kittitas County: +1.4% (+696)
- Klickitat County: +1.4% (+326)
3 of these 5 are also in the 2020–2025 top 10, so the growth is not a one-year blip.
Counties losing residents
2 of Washington's 39 counties had fewer residents in July 2025 than in April 2020. They are:
- Island County: −1.4% (−1,199, now about 85,657)
- Walla Walla County: −0.4% (−222, now about 62,361)
What fast growth means on a parcel map
- New lots show up as plats first. When land is subdivided, the plat is recorded with the county and the parcel layer catches up on its own schedule, so a brand-new lot may not appear on the map for a while. Check the recorder's recent plats if a parcel looks missing.
- Parcel numbers change after splits. A tract that was one parcel last year can be several today. Search by owner name or address as well as by an old parcel number.
- City limits move. Growing cities annex land, which changes who handles zoning and permits even though the county still keeps the deed and the tax map.
- Percent is not the same as people. A small county can post a big percentage on a modest number of new residents, so read the people-added column too.
Related guides
- Largest counties in Washington
- Washington county GIS websites by viewer
- Washington plat maps
- Washington statewide parcel map
- Washington landowner maps for hunting
- Fastest growing counties in the US
- US counties losing population
More: All Washington counties on Platbookmapper
Sources
- U.S. Census Bureau, Population Estimates Program, county totals, Vintage 2025 (April 1, 2020 estimates base and July 1, 2020–2025 estimates, with components of change). Percent change is from the April 1, 2020 estimates base to the July 1, 2025 estimate.
- Platbookmapper county GIS directory (live data file behind our county pages, pulled October 23, 2026) for each official parcel viewer.