Counties in Washington by population under 18

Adams County had the highest population under 18 of 39 counties in 2015, at 34.3%. Jefferson County had the lowest, at 13.4%. The median was 20.9% and the figure for Washington was 22.6%. Source: the U.S. Census Bureau.

Highest34.3Adams County

Lowest13.4Jefferson County

Median20.939 counties

Washington22.6History

Map of counties, 2015

Under 18
18 to 20
20 to 21
21 to 22
22 to 25
25 and over

%, 2015. Source: Invokely calculation with data from U.S. Census Bureau. Boundaries: U.S. Census Bureau cartographic boundary files.

All counties, 2015

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

Full ranking

Rank	Counties	2015 (%)	Change on 2014
1	Adams County	34.3	-0.1 pts
2	Franklin County	33.1	-0.2 pts
3	Grant County	29.8	-0.1 pts
4	Yakima County	29.4	-0.2 pts
5	Benton County	26.8	+0.1 pts
6	Douglas County	26.1	-0 pts
7	Clark County	25	-0.3 pts
8	Chelan County	23.8	-0.2 pts
9	Pierce County	23.7	-0.2 pts
10	Snohomish County	23.3	-0.1 pts
11	Cowlitz County	22.9	-0.1 pts
12	Okanogan County	22.6	-0.2 pts
13	Skagit County	22.5	-0.2 pts
14	Spokane County	22.4	-0.1 pts
15	Lewis County	22.2	+0.1 pts
16	Thurston County	22.2	-0.2 pts
17	Stevens County	22	-0.2 pts
18	Lincoln County	21.4	0 pts
19	Walla Walla County	21.4	-0.2 pts
20	Kitsap County	20.9	-0.2 pts
21	King County	20.9	-0.2 pts
22	Asotin County	20.7	-0.3 pts
23	Grays Harbor County	20.7	-0.2 pts
24	Whatcom County	20.3	-0.2 pts
25	Garfield County	20.2	+0.1 pts
26	Klickitat County	20.2	-0.4 pts
27	Skamania County	20.1	-0.8 pts
28	Pend Oreille County	19.6	-0 pts
29	Ferry County	19.4	-0.5 pts
30	Mason County	19.1	0 pts
31	Kittitas County	18.9	+0.1 pts
32	Island County	18.7	-0.4 pts
33	Columbia County	18.3	-0.8 pts
34	Pacific County	17.6	0 pts
35	Clallam County	17.5	-0.2 pts
36	Wahkiakum County	17.4	-0.5 pts
37	Whitman County	15.5	-0.1 pts
38	San Juan County	14.7	-0.3 pts
39	Jefferson County	13.4	-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, 2015) [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, 2015. 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=2015. 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, 2015. 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=2015.

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, 2015 [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=2015 (Accessed: 12 October 2026).

BibTeX

@misc{census_counties_in_washington_by_2015,
  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, 2015}},
  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=2015. 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, 2015
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=2015
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/rankings/population-under-18/washington-counties?period=2015.
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 34.3% in 2015, according to the U.S. Census Bureau.

Which county has the lowest population under 18?

Jefferson County, with 13.4% in 2015.

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.