Data / Rankings / Population aged 18 to 64 / Counties in Idaho

Counties in Idaho by population aged 18 to 64

Madison County had the highest population aged 18 to 64 of 44 counties in 2021, at 73%. Idaho County had the lowest, at 50.6%. The median was 54.5% and the figure for Idaho was 58.1%. Source: the U.S. Census Bureau.

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Highest73Madison County
Lowest50.6Idaho County
Median54.544 counties
Idaho58.1History

Map of counties, 2021

Ada County: 61.1 %Adams County: 51.7 %Bannock County: 58.5 %Bear Lake County: 51.1 %Benewah County: 52.4 %Bingham County: 54.7 %Blaine County: 57.1 %Boise County: 55.7 %Bonner County: 53.7 %Bonneville County: 56 %Boundary County: 50.8 %Butte County: 52.2 %Camas County: 54.3 %Canyon County: 57.6 %Caribou County: 52.6 %Cassia County: 53.8 %Clark County: 52.8 %Clearwater County: 54.4 %Custer County: 52.8 %Elmore County: 61.1 %Franklin County: 53.2 %Fremont County: 55.1 %Gem County: 53.4 %Gooding County: 54.6 %Idaho County: 50.6 %Jefferson County: 54.2 %Jerome County: 56.2 %Kootenai County: 56.6 %Latah County: 65.1 %Lemhi County: 50.7 %Lewis County: 51.8 %Lincoln County: 56.4 %Madison County: 73 %Minidoka County: 55.2 %Nez Perce County: 57.3 %Oneida County: 52 %Owyhee County: 55.7 %Payette County: 54 %Power County: 53.7 %Shoshone County: 54.9 %Teton County: 62 %Twin Falls County: 56.3 %Valley County: 54.8 %Washington County: 50.9 %
  • Under 52
  • 52 to 54
  • 54 to 56
  • 56 to 57
  • 57 and over
%, 2021. Source: Invokely calculation with data from U.S. Census Bureau. Boundaries: U.S. Census Bureau cartographic boundary files.

All counties, 2021

Madison County: 73 %Madison County73Latah County: 65.1 %Latah County65.1Teton County: 62 %Teton County62Elmore County: 61.1 %Elmore County61.1Ada County: 61.1 %Ada County61.1Bannock County: 58.5 %Bannock County58.5Canyon County: 57.6 %Canyon County57.6Nez Perce County: 57.3 %Nez Perce County57.3Blaine County: 57.1 %Blaine County57.1Kootenai County: 56.6 %Kootenai County56.6Lincoln County: 56.4 %Lincoln County56.4Twin Falls County: 56.3 %Twin Falls County56.3Jerome County: 56.2 %Jerome County56.2Bonneville County: 56 %Bonneville County56Boise County: 55.7 %Boise County55.7Owyhee County: 55.7 %Owyhee County55.7Minidoka County: 55.2 %Minidoka County55.2Fremont County: 55.1 %Fremont County55.1Shoshone County: 54.9 %Shoshone County54.9Valley County: 54.8 %Valley County54.8Bingham County: 54.7 %Bingham County54.7Gooding County: 54.6 %Gooding County54.6Clearwater County: 54.4 %Clearwater County54.4Camas County: 54.3 %Camas County54.3Jefferson County: 54.2 %Jefferson County54.2Payette County: 54 %Payette County54Cassia County: 53.8 %Cassia County53.8Bonner County: 53.7 %Bonner County53.7Power County: 53.7 %Power County53.7Gem County: 53.4 %Gem County53.4Franklin County: 53.2 %Franklin County53.2Clark County: 52.8 %Clark County52.8Custer County: 52.8 %Custer County52.8Caribou County: 52.6 %Caribou County52.6Benewah County: 52.4 %Benewah County52.4Butte County: 52.2 %Butte County52.2Oneida County: 52 %Oneida County52Lewis County: 51.8 %Lewis County51.8Adams County: 51.7 %Adams County51.7Bear Lake County: 51.1 %Bear Lake County51.1Washington County: 50.9 %Washington County50.9Boundary County: 50.8 %Boundary County50.8Lemhi County: 50.7 %Lemhi County50.7Idaho County: 50.6 %Idaho County50.6Madison County: 73 %Madison County73Latah County: 65.1 %Latah County65.1Teton County: 62 %Teton County62Elmore County: 61.1 %Elmore County61.1Ada County: 61.1 %Ada County61.1Bannock County: 58.5 %Bannock County58.5Canyon County: 57.6 %Canyon County57.6Nez Perce County: 57.3 %Nez Perce County57.3Blaine County: 57.1 %Blaine County57.1Kootenai County: 56.6 %Kootenai County56.6Lincoln County: 56.4 %Lincoln County56.4Twin Falls County: 56.3 %Twin Falls County56.3Jerome County: 56.2 %Jerome County56.2Bonneville County: 56 %Bonneville County56Boise County: 55.7 %Boise County55.7Owyhee County: 55.7 %Owyhee County55.7Minidoka County: 55.2 %Minidoka County55.2Fremont County: 55.1 %Fremont County55.1Shoshone County: 54.9 %Shoshone County54.9Valley County: 54.8 %Valley County54.8Bingham County: 54.7 %Bingham County54.7Gooding County: 54.6 %Gooding County54.6Clearwater County: 54.4 %Clearwater County54.4Camas County: 54.3 %Camas County54.3Jefferson County: 54.2 %Jefferson County54.2Payette County: 54 %Payette County54Cassia County: 53.8 %Cassia County53.8Bonner County: 53.7 %Bonner County53.7Power County: 53.7 %Power County53.7Gem County: 53.4 %Gem County53.4Franklin County: 53.2 %Franklin County53.2Clark County: 52.8 %Clark County52.8Custer County: 52.8 %Custer County52.8Caribou County: 52.6 %Caribou County52.6Benewah County: 52.4 %Benewah County52.4Butte County: 52.2 %Butte County52.2Oneida County: 52 %Oneida County52Lewis County: 51.8 %Lewis County51.8Adams County: 51.7 %Adams County51.7Bear Lake County: 51.1 %Bear Lake County51.1Washington County: 50.9 %Washington County50.9Boundary County: 50.8 %Boundary County50.8Lemhi County: 50.7 %Lemhi County50.7Idaho County: 50.6 %Idaho County50.6
%. Source: Invokely calculation with data from U.S. Census Bureau. Retrieved 2026-10-12.

Full ranking

RankCounties2021 (%)Change on 2020
1Madison County73-0.2 pts
2Latah County65.1-0.6 pts
3Teton County62+0.4 pts
4Elmore County61.1+0.1 pts
5Ada County61.1+0.1 pts
6Bannock County58.5+0.1 pts
7Canyon County57.6+0.4 pts
8Nez Perce County57.3-0.1 pts
9Blaine County57.1-0.2 pts
10Kootenai County56.6-0 pts
11Lincoln County56.4+0.6 pts
12Twin Falls County56.3+0.1 pts
13Jerome County56.2+0.2 pts
14Bonneville County56+0.2 pts
15Boise County55.7-0.8 pts
16Owyhee County55.7+0.3 pts
17Minidoka County55.20 pts
18Fremont County55.1+0.4 pts
19Shoshone County54.9-0.2 pts
20Valley County54.8-0 pts
21Bingham County54.70 pts
22Gooding County54.6+0.2 pts
23Clearwater County54.4-0.4 pts
24Camas County54.3-1.5 pts
25Jefferson County54.2+0.1 pts
26Payette County54-0 pts
27Cassia County53.8-0.1 pts
28Bonner County53.7-0.3 pts
29Power County53.7+0.2 pts
30Gem County53.4+0.2 pts
31Franklin County53.2+0.1 pts
32Clark County52.8-0.8 pts
33Custer County52.8+0.3 pts
34Caribou County52.6-0.3 pts
35Benewah County52.4-0.3 pts
36Butte County52.2-0.2 pts
37Oneida County520 pts
38Lewis County51.8-0.9 pts
39Adams County51.7-0.5 pts
40Bear Lake County51.10 pts
41Washington County50.9+0.2 pts
42Boundary County50.8+0.3 pts
43Lemhi County50.7+0.5 pts
44Idaho County50.6-0.2 pts

Other periods

About this ranking

Residents aged 18 to 64 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.

Not comparable with working-age shares for ages 15 to 64 used in EU and World Bank statistics.

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 18 to 64 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 18 to 64 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 aged 18 to 64, 2021) [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 18 to 64 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 aged 18 to 64, 2021. U.S. Census Bureau, 25 June 2026, https://www.census.gov/programs-surveys/popest/data/data-sets.html. Invokely, https://invokely.ai/rankings/population-18-64/idaho-counties?period=2021. Accessed 12 Oct. 2026.

Chicago (author-date)

U.S. Census Bureau. 2026. Population Estimates Program, county population by age and sex: residents aged 18 to 64 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 aged 18 to 64, 2021. 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-18-64/idaho-counties?period=2021.

Harvard

U.S. Census Bureau (2026) Population Estimates Program, county population by age and sex: residents aged 18 to 64 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 aged 18 to 64, 2021 [Dataset]. Available at: https://www.census.gov/programs-surveys/popest/data/data-sets.html, via Invokely: https://invokely.ai/rankings/population-18-64/idaho-counties?period=2021 (Accessed: 12 October 2026).

BibTeX
@misc{census_counties_in_idaho_by_2021,
  author = {{U.S. Census Bureau}},
  title = {{Population Estimates Program, county population by age and sex: residents aged 18 to 64 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 aged 18 to 64, 2021}},
  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-18-64/idaho-counties?period=2021. Publisher attribution: U.S. Census Bureau. Population Estimates Program, county population by age and sex: residents aged 18 to 64 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 18 to 64 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 aged 18 to 64, 2021
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-18-64/idaho-counties?period=2021
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/rankings/population-18-64/idaho-counties?period=2021.
N1  - Publisher attribution: U.S. Census Bureau. Population Estimates Program, county population by age and sex: residents aged 18 to 64 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 aged 18 to 64?

Madison County, with 73% in 2021, according to the U.S. Census Bureau.

Which county has the lowest population aged 18 to 64?

Idaho County, with 50.6% in 2021.

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 18 to 64 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 aged 18 to 64: other rankings

Counties in Idaho: more rankings