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 2015, at 70.8%. Bear Lake County had the lowest, at 51.9%. The median was 55.6% and the figure for Idaho was 58.8%. Source: the U.S. Census Bureau.

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Highest70.8Madison County
Lowest51.9Bear Lake County
Median55.644 counties
Idaho58.8History

Map of counties, 2015

Ada County: 61.6 %Adams County: 56 %Bannock County: 59.8 %Bear Lake County: 51.9 %Benewah County: 55.3 %Bingham County: 54.9 %Blaine County: 59.1 %Boise County: 59.3 %Bonner County: 57.4 %Bonneville County: 56.2 %Boundary County: 54.5 %Butte County: 53.3 %Camas County: 55 %Canyon County: 56.9 %Caribou County: 53.2 %Cassia County: 53.7 %Clark County: 54.8 %Clearwater County: 56.7 %Custer County: 57.6 %Elmore County: 61.9 %Franklin County: 52.2 %Fremont County: 54.5 %Gem County: 54.7 %Gooding County: 55 %Idaho County: 54.7 %Jefferson County: 53.6 %Jerome County: 56.1 %Kootenai County: 58.5 %Latah County: 68.5 %Lemhi County: 53.5 %Lewis County: 54.4 %Lincoln County: 55.7 %Madison County: 70.8 %Minidoka County: 55.6 %Nez Perce County: 59 %Oneida County: 52 %Owyhee County: 56 %Payette County: 55 %Power County: 54.8 %Shoshone County: 57.5 %Teton County: 61.8 %Twin Falls County: 57.1 %Valley County: 59.1 %Washington County: 52.8 %
  • Under 54
  • 54 to 55
  • 55 to 56
  • 56 to 57
  • 57 to 59
  • 59 and over
%, 2015. Source: Invokely calculation with data from U.S. Census Bureau. Boundaries: U.S. Census Bureau cartographic boundary files.

All counties, 2015

Madison County: 70.8 %Madison County70.8Latah County: 68.5 %Latah County68.5Elmore County: 61.9 %Elmore County61.9Teton County: 61.8 %Teton County61.8Ada County: 61.6 %Ada County61.6Bannock County: 59.8 %Bannock County59.8Boise County: 59.3 %Boise County59.3Valley County: 59.1 %Valley County59.1Blaine County: 59.1 %Blaine County59.1Nez Perce County: 59 %Nez Perce County59Kootenai County: 58.5 %Kootenai County58.5Custer County: 57.6 %Custer County57.6Shoshone County: 57.5 %Shoshone County57.5Bonner County: 57.4 %Bonner County57.4Twin Falls County: 57.1 %Twin Falls County57.1Canyon County: 56.9 %Canyon County56.9Clearwater County: 56.7 %Clearwater County56.7Bonneville County: 56.2 %Bonneville County56.2Jerome County: 56.1 %Jerome County56.1Adams County: 56 %Adams County56Owyhee County: 56 %Owyhee County56Lincoln County: 55.7 %Lincoln County55.7Minidoka County: 55.6 %Minidoka County55.6Benewah County: 55.3 %Benewah County55.3Camas County: 55 %Camas County55Gooding County: 55 %Gooding County55Payette County: 55 %Payette County55Bingham County: 54.9 %Bingham County54.9Power County: 54.8 %Power County54.8Clark County: 54.8 %Clark County54.8Gem County: 54.7 %Gem County54.7Idaho County: 54.7 %Idaho County54.7Boundary County: 54.5 %Boundary County54.5Fremont County: 54.5 %Fremont County54.5Lewis County: 54.4 %Lewis County54.4Cassia County: 53.7 %Cassia County53.7Jefferson County: 53.6 %Jefferson County53.6Lemhi County: 53.5 %Lemhi County53.5Butte County: 53.3 %Butte County53.3Caribou County: 53.2 %Caribou County53.2Washington County: 52.8 %Washington County52.8Franklin County: 52.2 %Franklin County52.2Oneida County: 52 %Oneida County52Bear Lake County: 51.9 %Bear Lake County51.9Madison County: 70.8 %Madison County70.8Latah County: 68.5 %Latah County68.5Elmore County: 61.9 %Elmore County61.9Teton County: 61.8 %Teton County61.8Ada County: 61.6 %Ada County61.6Bannock County: 59.8 %Bannock County59.8Boise County: 59.3 %Boise County59.3Valley County: 59.1 %Valley County59.1Blaine County: 59.1 %Blaine County59.1Nez Perce County: 59 %Nez Perce County59Kootenai County: 58.5 %Kootenai County58.5Custer County: 57.6 %Custer County57.6Shoshone County: 57.5 %Shoshone County57.5Bonner County: 57.4 %Bonner County57.4Twin Falls County: 57.1 %Twin Falls County57.1Canyon County: 56.9 %Canyon County56.9Clearwater County: 56.7 %Clearwater County56.7Bonneville County: 56.2 %Bonneville County56.2Jerome County: 56.1 %Jerome County56.1Adams County: 56 %Adams County56Owyhee County: 56 %Owyhee County56Lincoln County: 55.7 %Lincoln County55.7Minidoka County: 55.6 %Minidoka County55.6Benewah County: 55.3 %Benewah County55.3Camas County: 55 %Camas County55Gooding County: 55 %Gooding County55Payette County: 55 %Payette County55Bingham County: 54.9 %Bingham County54.9Power County: 54.8 %Power County54.8Clark County: 54.8 %Clark County54.8Gem County: 54.7 %Gem County54.7Idaho County: 54.7 %Idaho County54.7Boundary County: 54.5 %Boundary County54.5Fremont County: 54.5 %Fremont County54.5Lewis County: 54.4 %Lewis County54.4Cassia County: 53.7 %Cassia County53.7Jefferson County: 53.6 %Jefferson County53.6Lemhi County: 53.5 %Lemhi County53.5Butte County: 53.3 %Butte County53.3Caribou County: 53.2 %Caribou County53.2Washington County: 52.8 %Washington County52.8Franklin County: 52.2 %Franklin County52.2Oneida County: 52 %Oneida County52Bear Lake County: 51.9 %Bear Lake County51.9
%. Source: Invokely calculation with data from U.S. Census Bureau. Retrieved 2026-10-12.

Full ranking

RankCounties2015 (%)Change on 2014
1Madison County70.8+0.3 pts
2Latah County68.5-0.8 pts
3Elmore County61.9+0.1 pts
4Teton County61.8-0.2 pts
5Ada County61.6-0.3 pts
6Bannock County59.8-0.3 pts
7Boise County59.3-0.6 pts
8Valley County59.1-0.4 pts
9Blaine County59.1-1.3 pts
10Nez Perce County59-0.2 pts
11Kootenai County58.5-0.5 pts
12Custer County57.6-1.5 pts
13Shoshone County57.5-0.8 pts
14Bonner County57.4-0.8 pts
15Twin Falls County57.1-0.3 pts
16Canyon County56.9-0.2 pts
17Clearwater County56.7-0.4 pts
18Bonneville County56.2-0.2 pts
19Jerome County56.1-0.5 pts
20Adams County56-1.3 pts
21Owyhee County56-0.4 pts
22Lincoln County55.7+0.1 pts
23Minidoka County55.6-0.1 pts
24Benewah County55.3-0.6 pts
25Camas County55-0.9 pts
26Gooding County550 pts
27Payette County55-0.4 pts
28Bingham County54.9-0.1 pts
29Power County54.8-0.3 pts
30Clark County54.8-0.7 pts
31Gem County54.7-0.1 pts
31Idaho County54.7-0.9 pts
33Boundary County54.5-1 pts
34Fremont County54.5+0.1 pts
35Lewis County54.40 pts
36Cassia County53.7-0.2 pts
37Jefferson County53.6-0.3 pts
38Lemhi County53.5-0.7 pts
39Butte County53.3-0.8 pts
40Caribou County53.2-0.5 pts
41Washington County52.8-0.8 pts
42Franklin County52.2+0.3 pts
43Oneida County52-1 pts
44Bear Lake County51.9-0.5 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, 2015) [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, 2015. 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=2015. 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, 2015. 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=2015.

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, 2015 [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=2015 (Accessed: 12 October 2026).

BibTeX
@misc{census_counties_in_idaho_by_2015,
  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, 2015}},
  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=2015. 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, 2015
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=2015
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/rankings/population-18-64/idaho-counties?period=2015.
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 70.8% in 2015, according to the U.S. Census Bureau.

Which county has the lowest population aged 18 to 64?

Bear Lake County, with 51.9% in 2015.

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