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 2024, at 31.3%. Clearwater County had the lowest, at 15.8%. The median was 23.5% and the figure for Idaho was 23.6%. Source: the U.S. Census Bureau.

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Highest31.3Jefferson County
Lowest15.8Clearwater County
Median23.544 counties
Idaho23.6History

Map of counties, 2024

Ada County: 21.4 %Adams County: 16.5 %Bannock County: 24.7 %Bear Lake County: 25.8 %Benewah County: 21.8 %Bingham County: 28.2 %Blaine County: 18.3 %Boise County: 16.2 %Bonner County: 19.6 %Bonneville County: 28.6 %Boundary County: 23.5 %Butte County: 23.5 %Camas County: 19.3 %Canyon County: 26.3 %Caribou County: 28.3 %Cassia County: 30 %Clark County: 25.6 %Clearwater County: 15.8 %Custer County: 17.4 %Elmore County: 23.7 %Franklin County: 29.8 %Fremont County: 24.9 %Gem County: 21.9 %Gooding County: 25.1 %Idaho County: 19.7 %Jefferson County: 31.3 %Jerome County: 29.3 %Kootenai County: 22.1 %Latah County: 19.9 %Lemhi County: 17.8 %Lewis County: 20.1 %Lincoln County: 26.5 %Madison County: 21.6 %Minidoka County: 27.3 %Nez Perce County: 20.6 %Oneida County: 27.7 %Owyhee County: 24.3 %Payette County: 24.9 %Power County: 27.8 %Shoshone County: 20.2 %Teton County: 21.5 %Twin Falls County: 25.7 %Valley County: 18.1 %Washington County: 21.5 %
  • Under 19
  • 19 to 21
  • 21 to 23
  • 23 to 25
  • 25 to 28
  • 28 and over
%, 2024. Source: Invokely calculation with data from U.S. Census Bureau. Boundaries: U.S. Census Bureau cartographic boundary files.

All counties, 2024

Jefferson County: 31.3 %Jefferson County31.3Cassia County: 30 %Cassia County30Franklin County: 29.8 %Franklin County29.8Jerome County: 29.3 %Jerome County29.3Bonneville County: 28.6 %Bonneville County28.6Caribou County: 28.3 %Caribou County28.3Bingham County: 28.2 %Bingham County28.2Power County: 27.8 %Power County27.8Oneida County: 27.7 %Oneida County27.7Minidoka County: 27.3 %Minidoka County27.3Lincoln County: 26.5 %Lincoln County26.5Canyon County: 26.3 %Canyon County26.3Bear Lake County: 25.8 %Bear Lake County25.8Twin Falls County: 25.7 %Twin Falls County25.7Clark County: 25.6 %Clark County25.6Gooding County: 25.1 %Gooding County25.1Payette County: 24.9 %Payette County24.9Fremont County: 24.9 %Fremont County24.9Bannock County: 24.7 %Bannock County24.7Owyhee County: 24.3 %Owyhee County24.3Elmore County: 23.7 %Elmore County23.7Butte County: 23.5 %Butte County23.5Boundary County: 23.5 %Boundary County23.5Kootenai County: 22.1 %Kootenai County22.1Gem County: 21.9 %Gem County21.9Benewah County: 21.8 %Benewah County21.8Madison County: 21.6 %Madison County21.6Washington County: 21.5 %Washington County21.5Teton County: 21.5 %Teton County21.5Ada County: 21.4 %Ada County21.4Nez Perce County: 20.6 %Nez Perce County20.6Shoshone County: 20.2 %Shoshone County20.2Lewis County: 20.1 %Lewis County20.1Latah County: 19.9 %Latah County19.9Idaho County: 19.7 %Idaho County19.7Bonner County: 19.6 %Bonner County19.6Camas County: 19.3 %Camas County19.3Blaine County: 18.3 %Blaine County18.3Valley County: 18.1 %Valley County18.1Lemhi County: 17.8 %Lemhi County17.8Custer County: 17.4 %Custer County17.4Adams County: 16.5 %Adams County16.5Boise County: 16.2 %Boise County16.2Clearwater County: 15.8 %Clearwater County15.8Jefferson County: 31.3 %Jefferson County31.3Cassia County: 30 %Cassia County30Franklin County: 29.8 %Franklin County29.8Jerome County: 29.3 %Jerome County29.3Bonneville County: 28.6 %Bonneville County28.6Caribou County: 28.3 %Caribou County28.3Bingham County: 28.2 %Bingham County28.2Power County: 27.8 %Power County27.8Oneida County: 27.7 %Oneida County27.7Minidoka County: 27.3 %Minidoka County27.3Lincoln County: 26.5 %Lincoln County26.5Canyon County: 26.3 %Canyon County26.3Bear Lake County: 25.8 %Bear Lake County25.8Twin Falls County: 25.7 %Twin Falls County25.7Clark County: 25.6 %Clark County25.6Gooding County: 25.1 %Gooding County25.1Payette County: 24.9 %Payette County24.9Fremont County: 24.9 %Fremont County24.9Bannock County: 24.7 %Bannock County24.7Owyhee County: 24.3 %Owyhee County24.3Elmore County: 23.7 %Elmore County23.7Butte County: 23.5 %Butte County23.5Boundary County: 23.5 %Boundary County23.5Kootenai County: 22.1 %Kootenai County22.1Gem County: 21.9 %Gem County21.9Benewah County: 21.8 %Benewah County21.8Madison County: 21.6 %Madison County21.6Washington County: 21.5 %Washington County21.5Teton County: 21.5 %Teton County21.5Ada County: 21.4 %Ada County21.4Nez Perce County: 20.6 %Nez Perce County20.6Shoshone County: 20.2 %Shoshone County20.2Lewis County: 20.1 %Lewis County20.1Latah County: 19.9 %Latah County19.9Idaho County: 19.7 %Idaho County19.7Bonner County: 19.6 %Bonner County19.6Camas County: 19.3 %Camas County19.3Blaine County: 18.3 %Blaine County18.3Valley County: 18.1 %Valley County18.1Lemhi County: 17.8 %Lemhi County17.8Custer County: 17.4 %Custer County17.4Adams County: 16.5 %Adams County16.5Boise County: 16.2 %Boise County16.2Clearwater County: 15.8 %Clearwater County15.8
%. Source: Invokely calculation with data from U.S. Census Bureau. Retrieved 2026-10-12.

Full ranking

RankCounties2024 (%)Change on 2023
1Jefferson County31.3-0.7 pts
2Cassia County30-0.4 pts
3Franklin County29.8-0.5 pts
4Jerome County29.3-0.3 pts
5Bonneville County28.6-0.5 pts
6Caribou County28.3-0.2 pts
7Bingham County28.2-0.6 pts
8Power County27.8-1 pts
9Oneida County27.7+0.2 pts
10Minidoka County27.3-0.5 pts
11Lincoln County26.5-0.2 pts
12Canyon County26.3-0.4 pts
13Bear Lake County25.8-0.7 pts
14Twin Falls County25.7-0.4 pts
15Clark County25.6-1.2 pts
16Gooding County25.1-0.7 pts
17Payette County24.9-0.2 pts
18Fremont County24.9-0.7 pts
19Bannock County24.7-0.5 pts
20Owyhee County24.3-1.1 pts
21Elmore County23.7-0.4 pts
22Butte County23.5-0.4 pts
23Boundary County23.5-0.3 pts
24Kootenai County22.1-0.1 pts
25Gem County21.9-0.4 pts
26Benewah County21.8-0.4 pts
27Madison County21.6+0.1 pts
28Washington County21.5-0.7 pts
29Teton County21.5-1 pts
30Ada County21.4-0.5 pts
31Nez Perce County20.6-0.3 pts
32Shoshone County20.2-0.3 pts
33Lewis County20.1-0.9 pts
34Latah County19.9-0.1 pts
35Idaho County19.7-0.3 pts
36Bonner County19.60 pts
37Camas County19.3-0.4 pts
38Blaine County18.3-0.6 pts
39Valley County18.1-0.1 pts
40Lemhi County17.8-0.4 pts
41Custer County17.4+0.4 pts
42Adams County16.5-0.9 pts
43Boise County16.2-0.5 pts
44Clearwater County15.8-0.5 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, 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 Idaho 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/idaho-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 Idaho 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/idaho-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 Idaho 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/idaho-counties?period=2024 (Accessed: 12 October 2026).

BibTeX
@misc{census_counties_in_idaho_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 Idaho 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/idaho-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 Idaho 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/idaho-counties?period=2024
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/rankings/population-under-18/idaho-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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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 31.3% in 2024, according to the U.S. Census Bureau.

Which county has the lowest population under 18?

Clearwater County, with 15.8% 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.

Population under 18: other rankings

Counties in Idaho: more rankings