Population Characteristics - Median age
(2018)
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data: click here.
| County Name | Median age
Rank | Median age |
| Adams | 1 | 55.0 |
| Lemhi | 2 | 53.1 |
| Boise | 3 | 53.0 |
| Custer | 4 | 52.7 |
| Clearwater | 5 | 50.5 |
| Idaho | 6 | 50.2 |
| Valley | 7 | 48.7 |
| Lewis | 8 | 48.6 |
| Bonner | 9 | 48.2 |
| Benewah | 10 | 46.2 |
| Shoshone | 11 | 46.2 |
| Washington | 12 | 46.1 |
| Camas | 13 | 45.7 |
| Boundary | 14 | 44.9 |
| Butte | 15 | 44.8 |
| Gem | 16 | 44.2 |
| Blaine | 17 | 43.7 |
| Nez Perce | 18 | 40.8 |
| Kootenai | 19 | 40.5 |
| Bear Lake | 20 | 40.0 |
| Oneida | 21 | 40.0 |
| Owyhee | 22 | 39.1 |
| Payette | 23 | 39.1 |
| Teton | 24 | 38.6 |
| Fremont | 25 | 38.0 |
| Clark | 26 | 37.9 |
| Caribou | 27 | 37.3 |
| Gooding | 28 | 37.3 |
| Ada | 29 | 37.2 |
| Lincoln | 30 | 36.0 |
| Minidoka | 31 | 35.1 |
| Twin Falls | 32 | 34.9 |
| Bingham | 33 | 34.1 |
| Bannock | 34 | 34.0 |
| Canyon | 35 | 34.0 |
| Franklin | 36 | 33.7 |
| Power | 37 | 33.3 |
| Jerome | 38 | 33.2 |
| Bonneville | 39 | 32.9 |
| Cassia | 40 | 32.6 |
| Elmore | 41 | 31.7 |
| Jefferson | 42 | 31.5 |
| Latah | 43 | 29.2 |
| Madison | 44 | 23.2 |
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