RANKING · 2020 CENSUS · 44 SHOWN OF 44

Oldest by median age, Idaho counties · 2020

Idaho counties ranked by median age of residents (2020 ACS). This list covers the 44 counties in Idaho that qualify, ranked against each other statewide. The median across all 44 is 39.4.

Flip the list · Youngest by median age, US counties →

IdahoAll states All rankings

SAME RANKING BYCities States Metros ZIP codes

RELATEDLargest foreign-born population Most residents with a disability Largest veteran population Most uninsured people Largest senior population Most unmarried people

YEAR1990 2000 2010 2020 2024

RANKPLACESTATEPOPMEDIAN AGEVS 2000

01Adams County, IDID5,01354.9+24%

02Custer County, IDID4,63654.0+31%

03Boise County, IDID8,54553.9+33%

04Lemhi County, IDID8,47452.6+23%

05Clearwater County, IDID9,11852.1+25%

06Idaho County, IDID17,87451.4+22%

07Valley County, IDID12,83149.5+14%

08Bonner County, IDID54,42049.3+21%

09Lewis County, IDID3,70448.8+15%

10Shoshone County, IDID14,13048.2+15%

11Benewah County, IDID10,50847.5+21%

12Camas County, IDID1,31647.0+18%

13Boundary County, IDID13,99746.9+22%

14Washington County, IDID11,58346.0+17%

15Blaine County, IDID25,51745.4+21%

16Gem County, IDID21,77344.1+18%

17Butte County, IDID2,78342.7+10%

18Kootenai County, IDID191,86441.2+14%

19Nez Perce County, IDID42,90540.9+7%

20Oneida County, IDID5,08540.3+12%

21Bear Lake County, IDID6,72740.1+12%

22Payette County, IDID27,82439.4+15%

23Owyhee County, IDID12,66138.8+18%

24Clark County, IDID78337.9+23%

25Fremont County, IDID14,20837.7+18%

26Teton County, IDID13,25437.7+20%

27Caribou County, IDID7,25237.5+7%

28Ada County, IDID546,14137.4+14%

29Gooding County, IDID16,44637.1+6%

30Lincoln County, IDID5,60336.5+6%

31Twin Falls County, IDID97,53935.8+3%

32Power County, IDID8,24635.3+12%

33Minidoka County, IDID22,91135.2+5%

34Bingham County, IDID51,15334.8+17%

35Bannock County, IDID91,59134.7+16%

36Canyon County, IDID275,12334.5+13%

37Franklin County, IDID15,88933.9+22%

38Jerome County, IDID26,36233.4+2%

39Bonneville County, IDID135,77133.1+4%

40Cassia County, IDID26,39733.1+6%

41Elmore County, IDID29,46532.7+12%

42Jefferson County, IDID35,29732.1+11%

43Latah County, IDID41,84231.0+11%

44Madison County, IDID55,17223.1+12%

SHOWING 1–44 OF 44

Download CSV (full list, 44 rows)

UPDATED 2026-09-11 · DATA: US CENSUS BUREAU DECENNIAL CENSUS