Data / Rankings / Median age / Counties in Idaho

Counties in Idaho by median age

Adams County had the highest median age of 44 counties in 2021, at 54.7 years. Madison County had the lowest, at 23.3 years. The median was 39.5 years and the figure for Idaho was 36.8 years. Source: the U.S. Census Bureau.

Highest54.7Adams County
Lowest23.3Madison County
Median39.544 counties
Idaho36.8History

All counties, 2021

CSVChart (SVG)

Adams CountyAdams County: 54.7 years54.7Boise CountyBoise County: 53.7 years53.7Custer CountyCuster County: 53.4 years53.4Lemhi CountyLemhi County: 52.8 years52.8Clearwater CountyClearwater County: 51 years51Valley CountyValley County: 50.2 years50.2Idaho CountyIdaho County: 50.1 years50.1Lewis CountyLewis County: 49 years49Bonner CountyBonner County: 48.2 years48.2Shoshone CountyShoshone County: 46.3 years46.3Benewah CountyBenewah County: 45.9 years45.9Washington CountyWashington County: 44.9 years44.9Gem CountyGem County: 44.7 years44.7Butte CountyButte County: 44.3 years44.3Camas CountyCamas County: 44 years44Blaine CountyBlaine County: 43.8 years43.8Boundary CountyBoundary County: 43.8 years43.8Oneida CountyOneida County: 41.6 years41.6Nez Perce CountyNez Perce County: 40.6 years40.6Kootenai CountyKootenai County: 40.4 years40.4Owyhee CountyOwyhee County: 40 years40Payette CountyPayette County: 40 years40Bear Lake CountyBear Lake County: 38.9 years38.9Teton CountyTeton County: 38.3 years38.3Gooding CountyGooding County: 38.2 years38.2Fremont CountyFremont County: 37.9 years37.9Ada CountyAda County: 37.7 years37.7Caribou CountyCaribou County: 37.5 years37.5Lincoln CountyLincoln County: 36.4 years36.4Power CountyPower County: 36.2 years36.2Twin Falls CountyTwin Falls County: 35.3 years35.3Minidoka CountyMinidoka County: 35.1 years35.1Bannock CountyBannock County: 34.5 years34.5Bingham CountyBingham County: 34.2 years34.2Canyon CountyCanyon County: 34.1 years34.1Clark CountyClark County: 33.8 years33.8Cassia CountyCassia County: 33.2 years33.2Franklin CountyFranklin County: 33.2 years33.2Bonneville CountyBonneville County: 33 years33Jerome CountyJerome County: 32.9 years32.9Elmore CountyElmore County: 32.6 years32.6Jefferson CountyJefferson County: 31.9 years31.9Latah CountyLatah County: 30.1 years30.1Madison CountyMadison County: 23.3 years23.3
years. Source: U.S. Census Bureau. Retrieved 2026-10-08.

Full ranking

RankCounties2021
years
1Adams County54.7
2Boise County53.7
3Custer County53.4
4Lemhi County52.8
5Clearwater County51
6Valley County50.2
7Idaho County50.1
8Lewis County49
9Bonner County48.2
10Shoshone County46.3
11Benewah County45.9
12Washington County44.9
13Gem County44.7
14Butte County44.3
15Camas County44
16Blaine County43.8
16Boundary County43.8
18Oneida County41.6
19Nez Perce County40.6
20Kootenai County40.4
21Owyhee County40
21Payette County40
23Bear Lake County38.9
24Teton County38.3
25Gooding County38.2
26Fremont County37.9
27Ada County37.7
28Caribou County37.5
29Lincoln County36.4
30Power County36.2
31Twin Falls County35.3
32Minidoka County35.1
33Bannock County34.5
34Bingham County34.2
35Canyon County34.1
36Clark County33.8
37Cassia County33.2
37Franklin County33.2
39Bonneville County33
40Jerome County32.9
41Elmore County32.6
42Jefferson County31.9
43Latah County30.1
44Madison County23.3

Other periods

About this ranking

Age that divides the resident population into two halves of equal size. Spain and the EU: on 1 January. United States: American Community Survey five-year estimate, where the period shown is the last year of the five-year span.

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. American Community Survey 5-year estimates, table B01002: median age, total population. https://www2.census.gov/programs-surveys/acs/summary_file/2021/table-based-SF/data/5YRData/acsdt5y2021-b01002.dat. Retrieved 2026-10-08.

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Questions

Which county has the highest median age?

Adams County, with 54.7 years in 2021, according to the U.S. Census Bureau.

Which county has the lowest median age?

Madison County, with 23.3 years 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, American Community Survey 5-year estimates, table B01002: median age, total population. Retrieved 2026-10-08.

Median age: other rankings

Counties in Idaho: more rankings