Counties in Washington by population under 18

Adams County had the highest population under 18 of 39 counties in 2024, at 32.9%. Jefferson County had the lowest, at 10.9%. The median was 19.9% and the figure for Washington was 20.7%. Source: the U.S. Census Bureau.

Highest32.9Adams County

Lowest10.9Jefferson County

Median19.939 counties

Washington20.7History

Map of counties, 2024

Under 17
17 to 19
19 to 20
20 to 21
21 to 22
22 and over

%, 2024. Source: Invokely calculation with data from U.S. Census Bureau. Boundaries: U.S. Census Bureau cartographic boundary files.

All counties, 2024

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

Full ranking

Rank	Counties	2024 (%)	Change on 2023
1	Adams County	32.9	-0.3 pts
2	Franklin County	29.5	-0.6 pts
3	Yakima County	27.2	-0.4 pts
4	Grant County	27.1	-0.5 pts
5	Benton County	25.1	-0.4 pts
6	Douglas County	22.7	-0.6 pts
7	Pierce County	22.3	-0.2 pts
8	Cowlitz County	22	-0.2 pts
9	Lewis County	22	-0.1 pts
10	Chelan County	21.8	-0.1 pts
11	Snohomish County	21.7	-0.2 pts
12	Garfield County	21.7	-0.4 pts
13	Clark County	21.5	-0.4 pts
14	Spokane County	20.9	-0.2 pts
15	Okanogan County	20.9	-0.5 pts
16	Lincoln County	20.9	+0.1 pts
17	Stevens County	20.7	-0.2 pts
18	Skagit County	20.6	-0.2 pts
19	Thurston County	20.3	-0.3 pts
20	Walla Walla County	19.9	-0.3 pts
21	Pend Oreille County	19.6	-0.1 pts
22	Asotin County	19.6	+0.1 pts
23	Ferry County	19.4	+0.3 pts
24	Grays Harbor County	19.2	-0.3 pts
25	Mason County	19.1	+0.1 pts
26	Kitsap County	19	-0.2 pts
27	King County	18.9	-0.3 pts
28	Klickitat County	18.1	-0.1 pts
29	Whatcom County	18	-0.4 pts
30	Kittitas County	17.3	0 pts
31	Skamania County	17.2	-0.3 pts
32	Columbia County	17	+0.2 pts
33	Island County	16.6	-0.2 pts
34	Wahkiakum County	16	-0.6 pts
35	Whitman County	15.9	-0.2 pts
36	Clallam County	15.4	-0.2 pts
37	Pacific County	15	-0.5 pts
38	San Juan County	12.9	-0.2 pts
39	Jefferson County	10.9	-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, 2024) [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, 2024. 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?period=2024. 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, 2024. 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?period=2024.

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, 2024 [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?period=2024 (Accessed: 12 October 2026).

BibTeX

@misc{census_counties_in_washington_by_2024,
  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, 2024}},
  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?period=2024. 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, 2024
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?period=2024
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/rankings/population-under-18/washington-counties?period=2024.
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 32.9% in 2024, according to the U.S. Census Bureau.

Which county has the lowest population under 18?

Jefferson County, with 10.9% in 2024.

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.