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 2018, at 72.7%. Bear Lake County had the lowest, at 51.2%. The median was 55.4% and the figure for Idaho was 58.3%. Source: the U.S. Census Bureau.

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Highest72.7Madison County
Lowest51.2Bear Lake County
Median55.444 counties
Idaho58.3History

Map of counties, 2018

Ada County: 61.2 %Adams County: 54 %Bannock County: 59.1 %Bear Lake County: 51.2 %Benewah County: 53 %Bingham County: 54.5 %Blaine County: 57.3 %Boise County: 58 %Bonner County: 55.4 %Bonneville County: 55.9 %Boundary County: 52.1 %Butte County: 52.7 %Camas County: 55.6 %Canyon County: 57 %Caribou County: 52.5 %Cassia County: 53.6 %Clark County: 57.6 %Clearwater County: 55.6 %Custer County: 55.3 %Elmore County: 61.4 %Franklin County: 53 %Fremont County: 54.6 %Gem County: 53.8 %Gooding County: 54.7 %Idaho County: 52.2 %Jefferson County: 53.9 %Jerome County: 56.1 %Kootenai County: 57.3 %Latah County: 66.5 %Lemhi County: 51.5 %Lewis County: 53.6 %Lincoln County: 55.9 %Madison County: 72.7 %Minidoka County: 55.5 %Nez Perce County: 58.4 %Oneida County: 51.3 %Owyhee County: 54.9 %Payette County: 54.4 %Power County: 53.6 %Shoshone County: 56.3 %Teton County: 61.1 %Twin Falls County: 56.5 %Valley County: 56.4 %Washington County: 51.5 %
  • Under 53
  • 53 to 54
  • 54 to 55
  • 55 to 56
  • 56 to 58
  • 58 and over
%, 2018. Source: Invokely calculation with data from U.S. Census Bureau. Boundaries: U.S. Census Bureau cartographic boundary files.

All counties, 2018

Madison County: 72.7 %Madison County72.7Latah County: 66.5 %Latah County66.5Elmore County: 61.4 %Elmore County61.4Ada County: 61.2 %Ada County61.2Teton County: 61.1 %Teton County61.1Bannock County: 59.1 %Bannock County59.1Nez Perce County: 58.4 %Nez Perce County58.4Boise County: 58 %Boise County58Clark County: 57.6 %Clark County57.6Blaine County: 57.3 %Blaine County57.3Kootenai County: 57.3 %Kootenai County57.3Canyon County: 57 %Canyon County57Twin Falls County: 56.5 %Twin Falls County56.5Valley County: 56.4 %Valley County56.4Shoshone County: 56.3 %Shoshone County56.3Jerome County: 56.1 %Jerome County56.1Lincoln County: 55.9 %Lincoln County55.9Bonneville County: 55.9 %Bonneville County55.9Clearwater County: 55.6 %Clearwater County55.6Camas County: 55.6 %Camas County55.6Minidoka County: 55.5 %Minidoka County55.5Bonner County: 55.4 %Bonner County55.4Custer County: 55.3 %Custer County55.3Owyhee County: 54.9 %Owyhee County54.9Gooding County: 54.7 %Gooding County54.7Fremont County: 54.6 %Fremont County54.6Bingham County: 54.5 %Bingham County54.5Payette County: 54.4 %Payette County54.4Adams County: 54 %Adams County54Jefferson County: 53.9 %Jefferson County53.9Gem County: 53.8 %Gem County53.8Cassia County: 53.6 %Cassia County53.6Lewis County: 53.6 %Lewis County53.6Power County: 53.6 %Power County53.6Franklin County: 53 %Franklin County53Benewah County: 53 %Benewah County53Butte County: 52.7 %Butte County52.7Caribou County: 52.5 %Caribou County52.5Idaho County: 52.2 %Idaho County52.2Boundary County: 52.1 %Boundary County52.1Washington County: 51.5 %Washington County51.5Lemhi County: 51.5 %Lemhi County51.5Oneida County: 51.3 %Oneida County51.3Bear Lake County: 51.2 %Bear Lake County51.2Madison County: 72.7 %Madison County72.7Latah County: 66.5 %Latah County66.5Elmore County: 61.4 %Elmore County61.4Ada County: 61.2 %Ada County61.2Teton County: 61.1 %Teton County61.1Bannock County: 59.1 %Bannock County59.1Nez Perce County: 58.4 %Nez Perce County58.4Boise County: 58 %Boise County58Clark County: 57.6 %Clark County57.6Blaine County: 57.3 %Blaine County57.3Kootenai County: 57.3 %Kootenai County57.3Canyon County: 57 %Canyon County57Twin Falls County: 56.5 %Twin Falls County56.5Valley County: 56.4 %Valley County56.4Shoshone County: 56.3 %Shoshone County56.3Jerome County: 56.1 %Jerome County56.1Lincoln County: 55.9 %Lincoln County55.9Bonneville County: 55.9 %Bonneville County55.9Clearwater County: 55.6 %Clearwater County55.6Camas County: 55.6 %Camas County55.6Minidoka County: 55.5 %Minidoka County55.5Bonner County: 55.4 %Bonner County55.4Custer County: 55.3 %Custer County55.3Owyhee County: 54.9 %Owyhee County54.9Gooding County: 54.7 %Gooding County54.7Fremont County: 54.6 %Fremont County54.6Bingham County: 54.5 %Bingham County54.5Payette County: 54.4 %Payette County54.4Adams County: 54 %Adams County54Jefferson County: 53.9 %Jefferson County53.9Gem County: 53.8 %Gem County53.8Cassia County: 53.6 %Cassia County53.6Lewis County: 53.6 %Lewis County53.6Power County: 53.6 %Power County53.6Franklin County: 53 %Franklin County53Benewah County: 53 %Benewah County53Butte County: 52.7 %Butte County52.7Caribou County: 52.5 %Caribou County52.5Idaho County: 52.2 %Idaho County52.2Boundary County: 52.1 %Boundary County52.1Washington County: 51.5 %Washington County51.5Lemhi County: 51.5 %Lemhi County51.5Oneida County: 51.3 %Oneida County51.3Bear Lake County: 51.2 %Bear Lake County51.2
%. Source: Invokely calculation with data from U.S. Census Bureau. Retrieved 2026-10-12.

Full ranking

RankCounties2018 (%)Change on 2017
1Madison County72.7+0.6 pts
2Latah County66.5-0.9 pts
3Elmore County61.40 pts
4Ada County61.2-0.1 pts
5Teton County61.1-0.8 pts
6Bannock County59.1-0.2 pts
7Nez Perce County58.4-0.3 pts
8Boise County58-0.2 pts
9Clark County57.6+0.6 pts
10Blaine County57.3-0.6 pts
11Kootenai County57.3-0.3 pts
12Canyon County57+0.1 pts
13Twin Falls County56.5-0.1 pts
14Valley County56.4-0.7 pts
15Shoshone County56.3-0.6 pts
16Jerome County56.1-0.1 pts
17Lincoln County55.9+0.8 pts
18Bonneville County55.9-0.1 pts
19Clearwater County55.6-0.1 pts
20Camas County55.6-0 pts
21Minidoka County55.5-0.1 pts
22Bonner County55.4-0.6 pts
23Custer County55.3+0.3 pts
24Owyhee County54.9-0.2 pts
25Gooding County54.7-0.1 pts
26Fremont County54.6+0.1 pts
27Bingham County54.5-0.1 pts
28Payette County54.4-0 pts
29Adams County54-0.4 pts
30Jefferson County53.9+0.1 pts
31Gem County53.8-0.3 pts
32Cassia County53.6-0.1 pts
33Lewis County53.6-0.2 pts
34Power County53.6-0.2 pts
35Franklin County53+0.4 pts
36Benewah County53-0.7 pts
37Butte County52.7-0.3 pts
38Caribou County52.5-0.4 pts
39Idaho County52.2-0.9 pts
40Boundary County52.1-1.3 pts
41Washington County51.5-0.4 pts
42Lemhi County51.5-0.7 pts
43Oneida County51.3+0.1 pts
44Bear Lake County51.2-0.1 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, 2018) [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, 2018. 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=2018. 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, 2018. 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=2018.

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, 2018 [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=2018 (Accessed: 12 October 2026).

BibTeX
@misc{census_counties_in_idaho_by_2018,
  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, 2018}},
  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=2018. 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, 2018
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=2018
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/rankings/population-18-64/idaho-counties?period=2018.
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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Rank Counties in Idaho by population aged 18 to 64 using official data, and cite the source.
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Questions

Which county has the highest population aged 18 to 64?

Madison County, with 72.7% in 2018, according to the U.S. Census Bureau.

Which county has the lowest population aged 18 to 64?

Bear Lake County, with 51.2% in 2018.

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