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 2020, at 73.2%. Lemhi County had the lowest, at 50.2%. The median was 54.7% and the figure for Idaho was 58%. Source: the U.S. Census Bureau.

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Highest73.2Madison County
Lowest50.2Lemhi County
Median54.744 counties
Idaho58History

Map of counties, 2020

Ada County: 61 %Adams County: 52.2 %Bannock County: 58.5 %Bear Lake County: 51 %Benewah County: 52.7 %Bingham County: 54.7 %Blaine County: 57.2 %Boise County: 56.5 %Bonner County: 54 %Bonneville County: 55.8 %Boundary County: 50.4 %Butte County: 52.4 %Camas County: 55.8 %Canyon County: 57.2 %Caribou County: 52.9 %Cassia County: 53.9 %Clark County: 53.6 %Clearwater County: 54.8 %Custer County: 52.5 %Elmore County: 61 %Franklin County: 53.1 %Fremont County: 54.7 %Gem County: 53.2 %Gooding County: 54.3 %Idaho County: 50.8 %Jefferson County: 54.1 %Jerome County: 55.9 %Kootenai County: 56.6 %Latah County: 65.8 %Lemhi County: 50.2 %Lewis County: 52.6 %Lincoln County: 55.8 %Madison County: 73.2 %Minidoka County: 55.2 %Nez Perce County: 57.5 %Oneida County: 52 %Owyhee County: 55.4 %Payette County: 54.1 %Power County: 53.5 %Shoshone County: 55.1 %Teton County: 61.6 %Twin Falls County: 56.2 %Valley County: 54.8 %Washington County: 50.7 %
  • Under 52
  • 52 to 54
  • 54 to 55
  • 55 to 56
  • 56 to 57
  • 57 and over
%, 2020. Source: Invokely calculation with data from U.S. Census Bureau. Boundaries: U.S. Census Bureau cartographic boundary files.

All counties, 2020

Madison County: 73.2 %Madison County73.2Latah County: 65.8 %Latah County65.8Teton County: 61.6 %Teton County61.6Ada County: 61 %Ada County61Elmore County: 61 %Elmore County61Bannock County: 58.5 %Bannock County58.5Nez Perce County: 57.5 %Nez Perce County57.5Blaine County: 57.2 %Blaine County57.2Canyon County: 57.2 %Canyon County57.2Kootenai County: 56.6 %Kootenai County56.6Boise County: 56.5 %Boise County56.5Twin Falls County: 56.2 %Twin Falls County56.2Jerome County: 55.9 %Jerome County55.9Bonneville County: 55.8 %Bonneville County55.8Lincoln County: 55.8 %Lincoln County55.8Camas County: 55.8 %Camas County55.8Owyhee County: 55.4 %Owyhee County55.4Minidoka County: 55.2 %Minidoka County55.2Shoshone County: 55.1 %Shoshone County55.1Valley County: 54.8 %Valley County54.8Clearwater County: 54.8 %Clearwater County54.8Fremont County: 54.7 %Fremont County54.7Bingham County: 54.7 %Bingham County54.7Gooding County: 54.3 %Gooding County54.3Jefferson County: 54.1 %Jefferson County54.1Payette County: 54.1 %Payette County54.1Bonner County: 54 %Bonner County54Cassia County: 53.9 %Cassia County53.9Clark County: 53.6 %Clark County53.6Power County: 53.5 %Power County53.5Gem County: 53.2 %Gem County53.2Franklin County: 53.1 %Franklin County53.1Caribou County: 52.9 %Caribou County52.9Benewah County: 52.7 %Benewah County52.7Lewis County: 52.6 %Lewis County52.6Custer County: 52.5 %Custer County52.5Butte County: 52.4 %Butte County52.4Adams County: 52.2 %Adams County52.2Oneida County: 52 %Oneida County52Bear Lake County: 51 %Bear Lake County51Idaho County: 50.8 %Idaho County50.8Washington County: 50.7 %Washington County50.7Boundary County: 50.4 %Boundary County50.4Lemhi County: 50.2 %Lemhi County50.2Madison County: 73.2 %Madison County73.2Latah County: 65.8 %Latah County65.8Teton County: 61.6 %Teton County61.6Ada County: 61 %Ada County61Elmore County: 61 %Elmore County61Bannock County: 58.5 %Bannock County58.5Nez Perce County: 57.5 %Nez Perce County57.5Blaine County: 57.2 %Blaine County57.2Canyon County: 57.2 %Canyon County57.2Kootenai County: 56.6 %Kootenai County56.6Boise County: 56.5 %Boise County56.5Twin Falls County: 56.2 %Twin Falls County56.2Jerome County: 55.9 %Jerome County55.9Bonneville County: 55.8 %Bonneville County55.8Lincoln County: 55.8 %Lincoln County55.8Camas County: 55.8 %Camas County55.8Owyhee County: 55.4 %Owyhee County55.4Minidoka County: 55.2 %Minidoka County55.2Shoshone County: 55.1 %Shoshone County55.1Valley County: 54.8 %Valley County54.8Clearwater County: 54.8 %Clearwater County54.8Fremont County: 54.7 %Fremont County54.7Bingham County: 54.7 %Bingham County54.7Gooding County: 54.3 %Gooding County54.3Jefferson County: 54.1 %Jefferson County54.1Payette County: 54.1 %Payette County54.1Bonner County: 54 %Bonner County54Cassia County: 53.9 %Cassia County53.9Clark County: 53.6 %Clark County53.6Power County: 53.5 %Power County53.5Gem County: 53.2 %Gem County53.2Franklin County: 53.1 %Franklin County53.1Caribou County: 52.9 %Caribou County52.9Benewah County: 52.7 %Benewah County52.7Lewis County: 52.6 %Lewis County52.6Custer County: 52.5 %Custer County52.5Butte County: 52.4 %Butte County52.4Adams County: 52.2 %Adams County52.2Oneida County: 52 %Oneida County52Bear Lake County: 51 %Bear Lake County51Idaho County: 50.8 %Idaho County50.8Washington County: 50.7 %Washington County50.7Boundary County: 50.4 %Boundary County50.4Lemhi County: 50.2 %Lemhi County50.2
%. Source: Invokely calculation with data from U.S. Census Bureau. Retrieved 2026-10-12.

Full ranking

RankCounties2020 (%)Change on 2019
1Madison County73.20 pts
2Latah County65.8-0.3 pts
3Teton County61.6+0.5 pts
4Ada County61-0 pts
5Elmore County610 pts
6Bannock County58.5-0.3 pts
7Nez Perce County57.5-0.4 pts
8Blaine County57.20 pts
9Canyon County57.20 pts
10Kootenai County56.6-0.3 pts
11Boise County56.5-0.6 pts
12Twin Falls County56.2-0.1 pts
13Jerome County55.9+0.2 pts
14Bonneville County55.8-0.2 pts
15Lincoln County55.8-0.5 pts
16Camas County55.8+0.1 pts
17Owyhee County55.4+0.2 pts
18Minidoka County55.2-0.2 pts
19Shoshone County55.1-1 pts
20Valley County54.8-0.7 pts
21Clearwater County54.8-0.7 pts
22Fremont County54.7-0 pts
23Bingham County54.7+0.2 pts
24Gooding County54.3-0.5 pts
25Jefferson County54.10 pts
26Payette County54.1-0.2 pts
27Bonner County54-0.6 pts
28Cassia County53.9+0.2 pts
29Clark County53.6-3.9 pts
30Power County53.5-0.2 pts
31Gem County53.2-0.5 pts
32Franklin County53.1+0.2 pts
33Caribou County52.9+0.4 pts
34Benewah County52.7-0.1 pts
35Lewis County52.6-1.7 pts
36Custer County52.5-2 pts
37Butte County52.4+0.4 pts
38Adams County52.2-1.2 pts
39Oneida County52+0.9 pts
40Bear Lake County51-0 pts
41Idaho County50.8-0.9 pts
42Washington County50.7-0.5 pts
43Boundary County50.4-0.8 pts
44Lemhi County50.2-0.8 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, 2020) [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, 2020. 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=2020. 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, 2020. 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=2020.

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, 2020 [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=2020 (Accessed: 12 October 2026).

BibTeX
@misc{census_counties_in_idaho_by_2020,
  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, 2020}},
  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=2020. 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, 2020
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=2020
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/rankings/population-18-64/idaho-counties?period=2020.
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 73.2% in 2020, according to the U.S. Census Bureau.

Which county has the lowest population aged 18 to 64?

Lemhi County, with 50.2% in 2020.

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