Counties in Idaho by median age on 1 July (US county estimates), 2025

Boise County had the highest median age on 1 July (US county estimates) of 44 counties in 2025, at 54.3 years. Madison County had the lowest, at 22.5 years. The median was 40 years. Source: the U.S. Census Bureau.

Highest54.3Boise County

Lowest22.5Madison County

Median4044 counties

Map of counties, 2025

Under 35
35 to 37
37 to 40
40 to 45
45 to 50
50 and over

years, 2025. Source: U.S. Census Bureau, Population Estimates Program, county population by age and sex: median age (MEDIAN_AGE_TOT) on 1 July, 2010 to 2019 from the 2010 to 2020 intercensal file and 2020 onwards from the latest vintage. Boundaries: U.S. Census Bureau cartographic boundary files.

All counties, 2025

years. Source: U.S. Census Bureau, Population Estimates Program, county population by age and sex: median age (MEDIAN_AGE_TOT) on 1 July, 2010 to 2019 from the 2010 to 2020 intercensal file and 2020 onwards from the latest vintage. Retrieved 2026-10-12.

Full ranking

Rank	Counties	2025 years	Change on 2024
1	Boise County	54.3	+0.7
2	Adams County	53.4	+0.4
3	Custer County	52.1	-0.2
4	Lemhi County	51.8	-0.6
5	Clearwater County	51.6	-0.2
6	Idaho County	50.5	0
7	Valley County	50.2	+0.5
8	Camas County	50.1	+0.1
9	Bonner County	48.1	0
10	Lewis County	47.4	+0.1
11	Blaine County	46.5	+0.4
12	Washington County	46.1	+0.3
13	Benewah County	45.8	+0.1
14	Shoshone County	45.6	-0.4
15	Butte County	45	0
15	Gem County	45	+0.1
17	Boundary County	44.9	-0.1
18	Nez Perce County	42.1	0
19	Kootenai County	41.9	+0.2
20	Bear Lake County	41.6	+0.2
21	Teton County	40.9	+0.6
22	Payette County	40.2	+0.4
23	Owyhee County	39.7	+0.6
24	Clark County	39.3	-0.4
25	Ada County	39.1	+0.2
25	Oneida County	39.1	-0.2
27	Fremont County	38.5	+0.5
28	Gooding County	38	+0.2
29	Caribou County	37.8	-0.2
30	Twin Falls County	36.9	+0.1
31	Bingham County	35.8	+0.3
31	Lincoln County	35.8	+0.6
33	Bannock County	35.6	+0.2
33	Power County	35.6	+0.5
35	Minidoka County	35.5	+0.1
36	Canyon County	35.2	+0.2
37	Franklin County	34.6	+0.2
38	Elmore County	34.5	+0.4
39	Bonneville County	34.2	+0.1
39	Jerome County	34.2	+0.1
41	Jefferson County	34.1	+0.6
42	Cassia County	33.1	0
43	Latah County	31.6	+0.3
44	Madison County	22.5	0

Other periods

About this ranking

Age that divides the resident population of a US county into two halves of equal size on 1 July, from Census Bureau population estimates calculated by single year of age.

Counties only: the county file has no state or national medians, and medians cannot be added up. A single-year estimate, unlike median_age, which for US places is a five-year American Community Survey estimate.

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: median age (MEDIAN_AGE_TOT) on 1 July, 2010 to 2019 from the 2010 to 2020 intercensal file and 2020 onwards from the latest vintage. 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: median age (MEDIAN_AGE_TOT) on 1 July, 2010 to 2019 from the 2010 to 2020 intercensal file and 2020 onwards from the latest vintage (Counties in Idaho by median age on 1 July (US county estimates), 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: median age (MEDIAN_AGE_TOT) on 1 July, 2010 to 2019 from the 2010 to 2020 intercensal file and 2020 onwards from the latest vintage, Counties in Idaho by median age on 1 July (US county estimates), 2025. U.S. Census Bureau, 25 June 2026, https://www.census.gov/programs-surveys/popest/data/data-sets.html. Invokely, https://invokely.ai/rankings/median-age-july-1-us-counties/idaho-counties. Accessed 12 Oct. 2026.

Chicago (author-date)

U.S. Census Bureau. 2026. Population Estimates Program, county population by age and sex: median age (MEDIAN_AGE_TOT) on 1 July, 2010 to 2019 from the 2010 to 2020 intercensal file and 2020 onwards from the latest vintage. Counties in Idaho by median age on 1 July (US county estimates), 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/median-age-july-1-us-counties/idaho-counties.

Harvard

U.S. Census Bureau (2026) Population Estimates Program, county population by age and sex: median age (MEDIAN_AGE_TOT) on 1 July, 2010 to 2019 from the 2010 to 2020 intercensal file and 2020 onwards from the latest vintage, Counties in Idaho by median age on 1 July (US county estimates), 2025 [Dataset]. Available at: https://www.census.gov/programs-surveys/popest/data/data-sets.html, via Invokely: https://invokely.ai/rankings/median-age-july-1-us-counties/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: median age (MEDIAN\_AGE\_TOT) on 1 July, 2010 to 2019 from the 2010 to 2020 intercensal file and 2020 onwards from the latest vintage: Counties in Idaho by median age on 1 July (US county estimates), 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/median-age-july-1-us-counties/idaho-counties. Publisher attribution: U.S. Census Bureau. Population Estimates Program, county population by age and sex: median age (MEDIAN\_AGE\_TOT) on 1 July, 2010 to 2019 from the 2010 to 2020 intercensal file and 2020 onwards from the latest vintage. 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: median age (MEDIAN_AGE_TOT) on 1 July, 2010 to 2019 from the 2010 to 2020 intercensal file and 2020 onwards from the latest vintage: Counties in Idaho by median age on 1 July (US county estimates), 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/median-age-july-1-us-counties/idaho-counties
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/rankings/median-age-july-1-us-counties/idaho-counties.
N1  - Publisher attribution: U.S. Census Bureau. Population Estimates Program, county population by age and sex: median age (MEDIAN_AGE_TOT) on 1 July, 2010 to 2019 from the 2010 to 2020 intercensal file and 2020 onwards from the latest vintage. 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 median age on 1 July (US county estimates)?

Boise County, with 54.3 years in 2025, according to the U.S. Census Bureau.

Which county has the lowest median age on 1 July (US county estimates)?

Madison County, with 22.5 years 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: median age (MEDIAN_AGE_TOT) on 1 July, 2010 to 2019 from the 2010 to 2020 intercensal file and 2020 onwards from the latest vintage. Retrieved 2026-10-12.