Counties in Washington by population under 18, 2025

Adams County had the highest population under 18 of 39 counties in 2025, at 32.7%. Jefferson County had the lowest, at 10.7%. The median was 19.8% and the figure for Washington was 20.4%. Source: the U.S. Census Bureau.

Highest32.7Adams County

Lowest10.7Jefferson County

Median19.839 counties

Washington20.4History

All counties, 2025

%. Source: Invokely calculation with data from U.S. Census Bureau. Retrieved 2026-10-12.

Full ranking

Rank	Counties	2025 (%)	Change on 2024
1	Adams County	32.7	-0.2 pts
2	Franklin County	28.9	-0.6 pts
3	Yakima County	26.7	-0.5 pts
4	Grant County	26.7	-0.4 pts
5	Benton County	24.7	-0.4 pts
6	Douglas County	22.3	-0.4 pts
7	Pierce County	22	-0.2 pts
8	Cowlitz County	21.9	-0.1 pts
9	Lewis County	21.8	-0.2 pts
10	Garfield County	21.6	-0 pts
11	Chelan County	21.6	-0.1 pts
12	Snohomish County	21.5	-0.2 pts
13	Clark County	21.1	-0.4 pts
14	Lincoln County	20.9	0 pts
15	Spokane County	20.7	-0.2 pts
16	Stevens County	20.5	-0.2 pts
17	Okanogan County	20.3	-0.6 pts
18	Skagit County	20.2	-0.4 pts
19	Thurston County	20	-0.3 pts
20	Pend Oreille County	19.8	+0.1 pts
21	Asotin County	19.7	+0.1 pts
22	Walla Walla County	19.6	-0.2 pts
23	Ferry County	19.1	-0.3 pts
24	Grays Harbor County	19	-0.2 pts
25	Mason County	18.9	-0.1 pts
26	Kitsap County	18.7	-0.3 pts
27	King County	18.6	-0.3 pts
28	Klickitat County	18.2	0 pts
29	Whatcom County	17.7	-0.3 pts
30	Columbia County	17.3	+0.4 pts
31	Kittitas County	17.2	-0.1 pts
32	Skamania County	17.1	-0 pts
33	Island County	16.4	-0.2 pts
34	Wahkiakum County	15.9	-0 pts
35	Whitman County	15.7	-0.3 pts
36	Clallam County	15.3	-0.1 pts
37	Pacific County	14.9	-0.1 pts
38	San Juan County	12.5	-0.3 pts
39	Jefferson County	10.7	-0.2 pts

Other periods

About this ranking

Residents aged 0 to 17 as a percentage of total population on 1 July. United States: Census Bureau county population estimates by age; states and the nation are sums of their counties.

Uses the US age of majority. Not comparable with population_0_14_share, which stops at 14.

Every value in the ranking comes from the same publisher and the same period, so the counties are compared on one definition. Equal values share a rank.

How to cite

U.S. Census Bureau. Population Estimates Program, county population by age and sex: residents aged 0 to 17 as a percentage of the total on 1 July, 2010 to 2019 from the 2010 to 2020 intercensal file and 2020 onwards from the latest vintage; states and the nation summed from counties. https://www.census.gov/programs-surveys/popest/data/data-sets.html. Retrieved 2026-10-12.

Citation styles

The publisher is the author. Invokely is named only as the place the figures were read, where a style asks for it.

APA 7

U.S. Census Bureau. (2026). Population Estimates Program, county population by age and sex: residents aged 0 to 17 as a percentage of the total on 1 July, 2010 to 2019 from the 2010 to 2020 intercensal file and 2020 onwards from the latest vintage; states and the nation summed from counties (Counties in Washington by population under 18, 2025) [Data set]. Retrieved October 12, 2026, from https://www.census.gov/programs-surveys/popest/data/data-sets.html

MLA 9

Population Estimates Program, county population by age and sex: residents aged 0 to 17 as a percentage of the total on 1 July, 2010 to 2019 from the 2010 to 2020 intercensal file and 2020 onwards from the latest vintage; states and the nation summed from counties, Counties in Washington by population under 18, 2025. U.S. Census Bureau, 25 June 2026, https://www.census.gov/programs-surveys/popest/data/data-sets.html. Invokely, https://invokely.ai/rankings/population-under-18/washington-counties. Accessed 12 Oct. 2026.

Chicago (author-date)

U.S. Census Bureau. 2026. Population Estimates Program, county population by age and sex: residents aged 0 to 17 as a percentage of the total on 1 July, 2010 to 2019 from the 2010 to 2020 intercensal file and 2020 onwards from the latest vintage; states and the nation summed from counties. Counties in Washington by population under 18, 2025. Dataset. Accessed October 12, 2026. https://www.census.gov/programs-surveys/popest/data/data-sets.html. Also distributed by Invokely, https://invokely.ai/rankings/population-under-18/washington-counties.

Harvard

U.S. Census Bureau (2026) Population Estimates Program, county population by age and sex: residents aged 0 to 17 as a percentage of the total on 1 July, 2010 to 2019 from the 2010 to 2020 intercensal file and 2020 onwards from the latest vintage; states and the nation summed from counties, Counties in Washington by population under 18, 2025 [Dataset]. Available at: https://www.census.gov/programs-surveys/popest/data/data-sets.html, via Invokely: https://invokely.ai/rankings/population-under-18/washington-counties (Accessed: 12 October 2026).

BibTeX

@misc{census_counties_in_washington_by_2025,
  author = {{U.S. Census Bureau}},
  title = {{Population Estimates Program, county population by age and sex: residents aged 0 to 17 as a percentage of the total on 1 July, 2010 to 2019 from the 2010 to 2020 intercensal file and 2020 onwards from the latest vintage; states and the nation summed from counties: Counties in Washington by population under 18, 2025}},
  year = {2026},
  howpublished = {Data set},
  url = {https://www.census.gov/programs-surveys/popest/data/data-sets.html},
  urldate = {2026-10-12},
  note = {Accessed via Invokely, https://invokely.ai/rankings/population-under-18/washington-counties. Publisher attribution: U.S. Census Bureau. Population Estimates Program, county population by age and sex: residents aged 0 to 17 as a percentage of the total on 1 July, 2010 to 2019 from the 2010 to 2020 intercensal file and 2020 onwards from the latest vintage; states and the nation summed from counties. https://www.census.gov/programs-surveys/popest/data/data-sets.html. Retrieved 2026-10-12.},
}

RIS

TY  - DATA
AU  - U.S. Census Bureau
TI  - Population Estimates Program, county population by age and sex: residents aged 0 to 17 as a percentage of the total on 1 July, 2010 to 2019 from the 2010 to 2020 intercensal file and 2020 onwards from the latest vintage; states and the nation summed from counties: Counties in Washington by population under 18, 2025
PY  - 2026
DA  - 2026/06/25
PB  - U.S. Census Bureau
DB  - Invokely
UR  - https://www.census.gov/programs-surveys/popest/data/data-sets.html
L2  - https://invokely.ai/rankings/population-under-18/washington-counties
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/rankings/population-under-18/washington-counties.
N1  - Publisher attribution: U.S. Census Bureau. Population Estimates Program, county population by age and sex: residents aged 0 to 17 as a percentage of the total on 1 July, 2010 to 2019 from the 2010 to 2020 intercensal file and 2020 onwards from the latest vintage; states and the nation summed from counties. https://www.census.gov/programs-surveys/popest/data/data-sets.html. Retrieved 2026-10-12.
ER  -

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Questions

Which county has the highest population under 18?

Adams County, with 32.7% in 2025, according to the U.S. Census Bureau.

Which county has the lowest population under 18?

Jefferson County, with 10.7% in 2025.

Where does this ranking come from?

Every value comes from one source and one period, so the places are comparable: U.S. Census Bureau, Population Estimates Program, county population by age and sex: residents aged 0 to 17 as a percentage of the total on 1 July, 2010 to 2019 from the 2010 to 2020 intercensal file and 2020 onwards from the latest vintage; states and the nation summed from counties. Retrieved 2026-10-12.