| County | Rank | Change (2020) ↓ | 2025 Pop. | 2020 Pop. |
|---|---|---|---|---|
| Camas County | 1 | 25.28% | 1,358 | 1,084 |
| Oneida County | 2 | 17.81% | 5,379 | 4,566 |
| Canyon County | 3 | 16.4% | 271,238 | 233,013 |
| Boundary County | 4 | 16.38% | 14,127 | 12,139 |
| Adams County | 5 | 15.79% | 5,127 | 4,428 |
| Gem County | 6 | 15.74% | 22,305 | 19,272 |
| Bonner County | 7 | 15.66% | 54,827 | 47,403 |
| Jefferson County | 8 | 15.58% | 35,922 | 31,080 |
| Boise County | 9 | 15.23% | 8,831 | 7,664 |
| Washington County | 10 | 13.48% | 11,981 | 10,558 |
| Franklin County | 11 | 13.02% | 16,142 | 14,282 |
| Butte County | 12 | 11.38% | 2,878 | 2,584 |
| Idaho County | 13 | 10.86% | 18,396 | 16,594 |
| Valley County | 14 | 10.05% | 13,032 | 11,842 |
| Lemhi County | 15 | 9.96% | 8,755 | 7,962 |
| Benewah County | 16 | 9.91% | 10,525 | 9,576 |
| Clearwater County | 17 | 9.39% | 9,572 | 8,750 |
| Payette County | 18 | 9.34% | 27,979 | 25,590 |
| Kootenai County | 19 | 9.07% | 188,450 | 172,785 |
| Lincoln County | 20 | 8.69% | 5,580 | 5,134 |
| Fremont County | 21 | 8.46% | 14,554 | 13,419 |
| Twin Falls County | 22 | 8.25% | 97,826 | 90,372 |
| Bonneville County | 23 | 8.24% | 135,012 | 124,737 |
| Power County | 24 | 7.72% | 8,487 | 7,879 |
| Shoshone County | 25 | 7.64% | 14,208 | 13,199 |
| Ada County | 26 | 7.57% | 536,011 | 498,278 |
| Teton County | 27 | 7.45% | 12,609 | 11,735 |
| Bear Lake County | 28 | 7.4% | 6,838 | 6,367 |
| Owyhee County | 29 | 7.34% | 12,876 | 11,996 |
| Jerome County | 30 | 6.92% | 25,949 | 24,270 |
| Lewis County | 31 | 6.8% | 3,767 | 3,527 |
| Bingham County | 32 | 6.53% | 51,239 | 48,097 |
| Minidoka County | 33 | 6.26% | 23,024 | 21,668 |
| Custer County | 34 | 6.13% | 4,533 | 4,271 |
| Latah County | 35 | 6.1% | 42,055 | 39,638 |
| Elmore County | 36 | 6% | 30,390 | 28,669 |
| Bannock County | 37 | 5.36% | 91,950 | 87,276 |
| Gooding County | 38 | 4.96% | 16,425 | 15,649 |
| Cassia County | 39 | 4.2% | 25,800 | 24,760 |
| Blaine County | 40 | 4% | 25,321 | 24,348 |
| Caribou County | 41 | 3.48% | 7,257 | 7,013 |
| Nez Perce County | 42 | 2.37% | 43,143 | 42,145 |
| Madison County | 43 | 1.51% | 53,725 | 52,928 |
| Clark County | 44 | -1.14% | 783 | 792 |
Idaho's counties show varied growth patterns from 2020 to 2025. Camas County leads with 25.28% annualized growth, followed by Oneida County (17.81%) and Canyon County (16.4%). The largest counties are Ada County (536,011), Canyon County (271,238), and Kootenai County (188,450). Of the 44 counties in Idaho, 43 are growing while just 1 has experienced population decline. Overall, counties averaged 9.28% annualized growth, with total population growing by 9.02% annually.