Data / Rankings / Population under 18 / Counties in Idaho

Counties in Idaho by population under 18

Jefferson County had the highest population under 18 of 44 counties in 2023, at 32%. Clearwater County had the lowest, at 16.3%. The median was 23.9% and the figure for Idaho was 24%. Source: the U.S. Census Bureau.

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Highest32Jefferson County
Lowest16.3Clearwater County
Median23.944 counties
Idaho24History

Map of counties, 2023

Ada County: 21.9 %Adams County: 17.3 %Bannock County: 25.2 %Bear Lake County: 26.5 %Benewah County: 22.2 %Bingham County: 28.8 %Blaine County: 18.9 %Boise County: 16.7 %Bonner County: 19.5 %Bonneville County: 29.1 %Boundary County: 23.8 %Butte County: 23.9 %Camas County: 19.7 %Canyon County: 26.6 %Caribou County: 28.4 %Cassia County: 30.4 %Clark County: 26.8 %Clearwater County: 16.3 %Custer County: 17 %Elmore County: 24 %Franklin County: 30.3 %Fremont County: 25.6 %Gem County: 22.3 %Gooding County: 25.8 %Idaho County: 19.9 %Jefferson County: 32 %Jerome County: 29.6 %Kootenai County: 22.2 %Latah County: 20 %Lemhi County: 18.3 %Lewis County: 21 %Lincoln County: 26.7 %Madison County: 21.5 %Minidoka County: 27.9 %Nez Perce County: 20.8 %Oneida County: 27.5 %Owyhee County: 25.4 %Payette County: 25.1 %Power County: 28.8 %Shoshone County: 20.5 %Teton County: 22.5 %Twin Falls County: 26.1 %Valley County: 18.2 %Washington County: 22.2 %
  • Under 20
  • 20 to 22
  • 22 to 24
  • 24 to 26
  • 26 to 28
  • 28 and over
%, 2023. Source: Invokely calculation with data from U.S. Census Bureau. Boundaries: U.S. Census Bureau cartographic boundary files.

All counties, 2023

Jefferson County: 32 %Jefferson County32Cassia County: 30.4 %Cassia County30.4Franklin County: 30.3 %Franklin County30.3Jerome County: 29.6 %Jerome County29.6Bonneville County: 29.1 %Bonneville County29.1Power County: 28.8 %Power County28.8Bingham County: 28.8 %Bingham County28.8Caribou County: 28.4 %Caribou County28.4Minidoka County: 27.9 %Minidoka County27.9Oneida County: 27.5 %Oneida County27.5Clark County: 26.8 %Clark County26.8Lincoln County: 26.7 %Lincoln County26.7Canyon County: 26.6 %Canyon County26.6Bear Lake County: 26.5 %Bear Lake County26.5Twin Falls County: 26.1 %Twin Falls County26.1Gooding County: 25.8 %Gooding County25.8Fremont County: 25.6 %Fremont County25.6Owyhee County: 25.4 %Owyhee County25.4Bannock County: 25.2 %Bannock County25.2Payette County: 25.1 %Payette County25.1Elmore County: 24 %Elmore County24Butte County: 23.9 %Butte County23.9Boundary County: 23.8 %Boundary County23.8Teton County: 22.5 %Teton County22.5Gem County: 22.3 %Gem County22.3Benewah County: 22.2 %Benewah County22.2Kootenai County: 22.2 %Kootenai County22.2Washington County: 22.2 %Washington County22.2Ada County: 21.9 %Ada County21.9Madison County: 21.5 %Madison County21.5Lewis County: 21 %Lewis County21Nez Perce County: 20.8 %Nez Perce County20.8Shoshone County: 20.5 %Shoshone County20.5Latah County: 20 %Latah County20Idaho County: 19.9 %Idaho County19.9Camas County: 19.7 %Camas County19.7Bonner County: 19.5 %Bonner County19.5Blaine County: 18.9 %Blaine County18.9Lemhi County: 18.3 %Lemhi County18.3Valley County: 18.2 %Valley County18.2Adams County: 17.3 %Adams County17.3Custer County: 17 %Custer County17Boise County: 16.7 %Boise County16.7Clearwater County: 16.3 %Clearwater County16.3Jefferson County: 32 %Jefferson County32Cassia County: 30.4 %Cassia County30.4Franklin County: 30.3 %Franklin County30.3Jerome County: 29.6 %Jerome County29.6Bonneville County: 29.1 %Bonneville County29.1Power County: 28.8 %Power County28.8Bingham County: 28.8 %Bingham County28.8Caribou County: 28.4 %Caribou County28.4Minidoka County: 27.9 %Minidoka County27.9Oneida County: 27.5 %Oneida County27.5Clark County: 26.8 %Clark County26.8Lincoln County: 26.7 %Lincoln County26.7Canyon County: 26.6 %Canyon County26.6Bear Lake County: 26.5 %Bear Lake County26.5Twin Falls County: 26.1 %Twin Falls County26.1Gooding County: 25.8 %Gooding County25.8Fremont County: 25.6 %Fremont County25.6Owyhee County: 25.4 %Owyhee County25.4Bannock County: 25.2 %Bannock County25.2Payette County: 25.1 %Payette County25.1Elmore County: 24 %Elmore County24Butte County: 23.9 %Butte County23.9Boundary County: 23.8 %Boundary County23.8Teton County: 22.5 %Teton County22.5Gem County: 22.3 %Gem County22.3Benewah County: 22.2 %Benewah County22.2Kootenai County: 22.2 %Kootenai County22.2Washington County: 22.2 %Washington County22.2Ada County: 21.9 %Ada County21.9Madison County: 21.5 %Madison County21.5Lewis County: 21 %Lewis County21Nez Perce County: 20.8 %Nez Perce County20.8Shoshone County: 20.5 %Shoshone County20.5Latah County: 20 %Latah County20Idaho County: 19.9 %Idaho County19.9Camas County: 19.7 %Camas County19.7Bonner County: 19.5 %Bonner County19.5Blaine County: 18.9 %Blaine County18.9Lemhi County: 18.3 %Lemhi County18.3Valley County: 18.2 %Valley County18.2Adams County: 17.3 %Adams County17.3Custer County: 17 %Custer County17Boise County: 16.7 %Boise County16.7Clearwater County: 16.3 %Clearwater County16.3
%. Source: Invokely calculation with data from U.S. Census Bureau. Retrieved 2026-10-12.

Full ranking

RankCounties2023 (%)Change on 2022
1Jefferson County32-0.9 pts
2Cassia County30.4-0.3 pts
3Franklin County30.3-0.6 pts
4Jerome County29.6-0.2 pts
5Bonneville County29.1-0.5 pts
6Power County28.8-0.8 pts
7Bingham County28.8-0.7 pts
8Caribou County28.4-0.2 pts
9Minidoka County27.9-0.4 pts
10Oneida County27.5+0.2 pts
11Clark County26.8-1.5 pts
12Lincoln County26.7-0.5 pts
13Canyon County26.6-0.4 pts
14Bear Lake County26.5-1.2 pts
15Twin Falls County26.1-0.4 pts
16Gooding County25.8-0.7 pts
17Fremont County25.6-0.5 pts
18Owyhee County25.4-1 pts
19Bannock County25.2-0.4 pts
20Payette County25.1-0.5 pts
21Elmore County24-0.1 pts
22Butte County23.9-0.3 pts
23Boundary County23.8-0.2 pts
24Teton County22.5-1 pts
25Gem County22.3-0.4 pts
26Benewah County22.2-0.2 pts
27Kootenai County22.2-0.2 pts
28Washington County22.2-0.4 pts
29Ada County21.9-0.5 pts
30Madison County21.5+0.3 pts
31Lewis County21-0.9 pts
32Nez Perce County20.8-0.3 pts
33Shoshone County20.50 pts
34Latah County20+0.1 pts
35Idaho County19.9+0.3 pts
36Camas County19.7+0.1 pts
37Bonner County19.5-0.1 pts
38Blaine County18.9-0.5 pts
39Lemhi County18.30 pts
40Valley County18.2-0.1 pts
41Adams County17.3-0 pts
42Custer County17-0.4 pts
43Boise County16.7-0.3 pts
44Clearwater County16.3-0.1 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 Idaho by population under 18, 2023) [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 Idaho by population under 18, 2023. 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/idaho-counties?period=2023. 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 Idaho by population under 18, 2023. 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/idaho-counties?period=2023.

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 Idaho by population under 18, 2023 [Dataset]. Available at: https://www.census.gov/programs-surveys/popest/data/data-sets.html, via Invokely: https://invokely.ai/rankings/population-under-18/idaho-counties?period=2023 (Accessed: 12 October 2026).

BibTeX
@misc{census_counties_in_idaho_by_2023,
  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 Idaho by population under 18, 2023}},
  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/idaho-counties?period=2023. 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 Idaho by population under 18, 2023
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/idaho-counties?period=2023
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/rankings/population-under-18/idaho-counties?period=2023.
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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Rank Counties in Idaho by population under 18 using official data, and cite the source.
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Questions

Which county has the highest population under 18?

Jefferson County, with 32% in 2023, according to the U.S. Census Bureau.

Which county has the lowest population under 18?

Clearwater County, with 16.3% in 2023.

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.

Population under 18: other rankings

Counties in Idaho: more rankings