Counties in Idaho by population under 18, 2025
Jefferson County had the highest population under 18 of 44 counties in 2025, at 30.3%. Boise County had the lowest, at 15.4%. The median was 23.3% and the figure for Idaho was 23.3%. Source: the U.S. Census Bureau.
All counties, 2025
Full ranking
| Rank | Counties | 2025 (%) | Change on 2024 |
|---|---|---|---|
| 1 | Jefferson County | 30.3 | -0.9 pts |
| 2 | Cassia County | 29.5 | -0.5 pts |
| 3 | Franklin County | 29.4 | -0.4 pts |
| 4 | Jerome County | 29.1 | -0.2 pts |
| 5 | Bonneville County | 28 | -0.5 pts |
| 6 | Oneida County | 28 | +0.2 pts |
| 7 | Caribou County | 27.9 | -0.4 pts |
| 8 | Bingham County | 27.6 | -0.5 pts |
| 9 | Power County | 27.2 | -0.5 pts |
| 10 | Minidoka County | 27.1 | -0.2 pts |
| 11 | Clark County | 26.3 | +0.7 pts |
| 12 | Lincoln County | 26.2 | -0.3 pts |
| 13 | Canyon County | 25.8 | -0.5 pts |
| 14 | Twin Falls County | 25.2 | -0.5 pts |
| 15 | Bear Lake County | 25.1 | -0.7 pts |
| 16 | Gooding County | 24.6 | -0.5 pts |
| 17 | Bannock County | 24.4 | -0.3 pts |
| 18 | Payette County | 24.3 | -0.6 pts |
| 19 | Fremont County | 24.3 | -0.6 pts |
| 20 | Elmore County | 23.4 | -0.2 pts |
| 21 | Boundary County | 23.4 | -0.1 pts |
| 22 | Owyhee County | 23.3 | -1 pts |
| 23 | Butte County | 23.2 | -0.3 pts |
| 24 | Gem County | 21.9 | -0.1 pts |
| 25 | Kootenai County | 21.8 | -0.2 pts |
| 26 | Benewah County | 21.6 | -0.3 pts |
| 26 | Madison County | 21.6 | -0 pts |
| 28 | Ada County | 21 | -0.4 pts |
| 29 | Washington County | 20.9 | -0.6 pts |
| 30 | Teton County | 20.8 | -0.7 pts |
| 31 | Nez Perce County | 20.4 | -0.1 pts |
| 32 | Lewis County | 20.4 | +0.3 pts |
| 33 | Shoshone County | 20.4 | +0.2 pts |
| 34 | Latah County | 19.9 | -0.1 pts |
| 35 | Idaho County | 19.4 | -0.3 pts |
| 36 | Bonner County | 19.3 | -0.3 pts |
| 37 | Camas County | 19.3 | 0 pts |
| 38 | Lemhi County | 17.7 | -0.2 pts |
| 39 | Valley County | 17.5 | -0.5 pts |
| 40 | Blaine County | 17.5 | -0.8 pts |
| 41 | Custer County | 17 | -0.4 pts |
| 42 | Adams County | 16.1 | -0.4 pts |
| 43 | Clearwater County | 15.7 | -0 pts |
| 44 | Boise County | 15.4 | -0.8 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
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, 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 Idaho 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/idaho-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 Idaho 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/idaho-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 Idaho 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/idaho-counties (Accessed: 12 October 2026).
BibTeX
@misc{census_counties_in_idaho_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 Idaho 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/idaho-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 Idaho 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/idaho-counties
Y2 - 2026/10/12
N1 - Accessed via Invokely, https://invokely.ai/rankings/population-under-18/idaho-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 -
Use this data in your AI agent
Invokely serves this figure to AI assistants through MCP and to code through a REST API, with the source and citation attached. Ask your assistant:
Rank Counties in Idaho by population under 18 using official data, and cite the source.
rank_places {"indicator":"population_0_17_share","level":"province","within":"Idaho","limit":10}
GET https://invokely.ai/api/v1/rank?indicator=population_0_17_share&level=province&within=Idaho&limit=10Questions
Which county has the highest population under 18?
Jefferson County, with 30.3% in 2025, according to the U.S. Census Bureau.
Which county has the lowest population under 18?
Boise County, with 15.4% 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.