This is a 2.8 percent rise in Ada County’s population, from 497,984 in 2020 to 511,931 in 2021.
Ada County had the largest population in Idaho in 2021.
The US Census Bureau found more than 73 percent of counties in the US saw a natural decrease in population in 2021. This is up from a 55.5 percent increase in 2020.
The Midwest suffered the most sustained population decreases, with many counties along the US East Coast and through the Rocky Mountains seeing increases.
The US population continues to grow, though at a slower rate than before.
Idaho Counties By Population Change from 2020 to 2021
| County | 2020 Estimated Population | 2021 Estimated Population | % Change in Population From Year to Year |
|---|---|---|---|
| Boise County | 7,647 | 8,094 | 5.8% |
| Lewis County | 3,531 | 3,715 | 5.2% |
| Camas County | 1,089 | 1,139 | 4.6% |
| Teton County | 11,731 | 12,267 | 4.6% |
| Adams County | 4,424 | 4,625 | 4.5% |
| Canyon County | 232,714 | 243,115 | 4.5% |
| Bonner County | 47,390 | 49,491 | 4.4% |
| Kootenai County | 172,646 | 179,789 | 4.1% |
| Custer County | 4,266 | 4,428 | 3.8% |
| Benewah County | 9,576 | 9,931 | 3.7% |
| Boundary County | 12,113 | 12,561 | 3.7% |
| Jefferson County | 31,055 | 32,202 | 3.7% |
| Valley County | 11,838 | 12,241 | 3.4% |
| Washington County | 10,544 | 10,898 | 3.4% |
| Shoshone County | 13,189 | 13,612 | 3.2% |
| Owyhee County | 11,978 | 12,336 | 3% |
| Butte County | 2,577 | 2,654 | 3% |
| Payette County | 25,589 | 26,350 | 3% |
| Lincoln County | 5,133 | 5,282 | 2.9% |
| Idaho County | 16,561 | 17,040 | 2.9% |
| Ada County | 497,984 | 511,931 | 2.8% |
| Franklin County | 14,269 | 14,666 | 2.8% |
| Gem County | 19,258 | 19,792 | 2.8% |
| Bear Lake County | 6,370 | 6,545 | 2.7% |
| Lemhi County | 7,948 | 8,162 | 2.7% |
| Bonneville County | 124,626 | 127,930 | 2.7% |
| Twin Falls County | 90,279 | 92,243 | 2.2% |
| Madison County | 52,876 | 53,881 | 1.9% |
| Cassia County | 24,699 | 25,164 | 1.9% |
| Jerome County | 24,222 | 24,662 | 1.8% |
| Blaine County | 24,327 | 24,766 | 1.8% |
| Latah County | 39,611 | 40,313 | 1.8% |
| Bingham County | 48,068 | 48,876 | 1.7% |
| Clearwater County | 8,750 | 8,895 | 1.7% |
| Fremont County | 13,404 | 13,592 | 1.4% |
| Caribou County | 7,015 | 7,111 | 1.4% |
| Minidoka County | 21,674 | 21,955 | 1.3% |
| Oneida County | 4,554 | 4,611 | 1.3% |
| Bannock County | 87,177 | 88,263 | 1.2% |
| Power County | 7,879 | 7,950 | 0.9% |
| Nez Perce County | 42,088 | 42,454 | 0.9% |
| Gooding County | 15,643 | 15,772 | 0.8% |
| Elmore County | 28,668 | 28,827 | 0.6% |
| Clark County | 792 | 792 | 0% |
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