| County | Rank | Change (2020) ↓ | 2025 Pop. | 2020 Pop. |
|---|---|---|---|---|
| Dallas County | 1 | 18.45% | 119,093 | 100,544 |
| Warren County | 2 | 9.12% | 57,388 | 52,591 |
| Polk County | 3 | 6.46% | 524,883 | 493,039 |
| Johnson County | 4 | 5.82% | 161,958 | 153,052 |
| Story County | 5 | 4.91% | 103,495 | 98,651 |
| Lyon County | 6 | 4.57% | 12,468 | 11,923 |
| Madison County | 7 | 4.18% | 17,323 | 16,628 |
| Jones County | 8 | 3.2% | 21,315 | 20,654 |
| Wayne County | 9 | 3.08% | 6,702 | 6,502 |
| Marion County | 10 | 2.89% | 34,378 | 33,414 |
| Mills County | 11 | 2.59% | 14,792 | 14,418 |
| Dickinson County | 12 | 2.57% | 18,229 | 17,773 |
| Sioux County | 13 | 2.26% | 36,709 | 35,897 |
| O'Brien County | 14 | 2.15% | 14,453 | 14,149 |
| Woodbury County | 15 | 1.9% | 107,970 | 105,952 |
| Black Hawk County | 16 | 1.88% | 133,517 | 131,049 |
| Wapello County | 17 | 1.75% | 35,945 | 35,327 |
| Linn County | 18 | 1.6% | 234,122 | 230,433 |
| Franklin County | 19 | 1.58% | 10,153 | 9,995 |
| Guthrie County | 20 | 1.56% | 10,785 | 10,619 |
| Jefferson County | 21 | 1.51% | 15,936 | 15,699 |
| Lucas County | 22 | 1.4% | 8,741 | 8,620 |
| Bremer County | 23 | 1.38% | 25,352 | 25,007 |
| Mitchell County | 24 | 1.27% | 10,720 | 10,586 |
| Davis County | 25 | 1.16% | 9,221 | 9,115 |
| Marshall County | 26 | 1.15% | 40,554 | 40,091 |
| Scott County | 27 | 1.14% | 176,613 | 174,617 |
| Benton County | 28 | 1.09% | 25,829 | 25,550 |
| Jasper County | 29 | 1.07% | 38,223 | 37,818 |
| Delaware County | 30 | 1.04% | 17,635 | 17,454 |
| Allamakee County | 31 | 0.93% | 14,200 | 14,069 |
| Shelby County | 32 | 0.78% | 11,819 | 11,727 |
| Crawford County | 33 | 0.76% | 16,618 | 16,492 |
| Humboldt County | 34 | 0.76% | 9,670 | 9,597 |
| Plymouth County | 35 | 0.74% | 25,885 | 25,694 |
| Washington County | 36 | 0.74% | 22,708 | 22,541 |
| Boone County | 37 | 0.71% | 26,891 | 26,702 |
| Buchanan County | 38 | 0.66% | 20,741 | 20,606 |
| Buena Vista County | 39 | 0.61% | 20,934 | 20,808 |
| Clay County | 40 | 0.5% | 16,418 | 16,337 |
| Webster County | 41 | 0.47% | 37,165 | 36,991 |
| Grundy County | 42 | 0.41% | 12,398 | 12,347 |
| Harrison County | 43 | 0.32% | 14,614 | 14,567 |
| Dubuque County | 44 | 0.19% | 99,496 | 99,310 |
| Pottawattamie County | 45 | 0.05% | 93,705 | 93,655 |
| Cherokee County | 46 | 0.05% | 11,664 | 11,658 |
| Jackson County | 47 | -0.13% | 19,427 | 19,453 |
| Greene County | 48 | -0.26% | 8,727 | 8,750 |
| Mahaska County | 49 | -0.28% | 22,101 | 22,162 |
| Adair County | 50 | -0.35% | 7,463 | 7,489 |
| Fremont County | 51 | -0.56% | 6,530 | 6,567 |
| Van Buren County | 52 | -0.69% | 7,168 | 7,218 |
| Page County | 53 | -0.89% | 15,064 | 15,200 |
| Clayton County | 54 | -0.92% | 16,877 | 17,034 |
| Louisa County | 55 | -0.97% | 10,720 | 10,825 |
| Hamilton County | 56 | -0.98% | 14,864 | 15,011 |
| Des Moines County | 57 | -1.01% | 38,462 | 38,856 |
| Union County | 58 | -1.08% | 11,997 | 12,128 |
| Pocahontas County | 59 | -1.13% | 6,988 | 7,068 |
| Clinton County | 60 | -1.15% | 45,896 | 46,432 |
| Iowa County | 61 | -1.16% | 16,460 | 16,653 |
| Poweshiek County | 62 | -1.16% | 18,411 | 18,628 |
| Cerro Gordo County | 63 | -1.17% | 42,516 | 43,021 |
| Adams County | 64 | -1.37% | 3,659 | 3,710 |
| Howard County | 65 | -1.41% | 9,363 | 9,497 |
| Hancock County | 66 | -1.46% | 10,601 | 10,758 |
| Cass County | 67 | -1.51% | 12,917 | 13,115 |
| Audubon County | 68 | -1.57% | 5,591 | 5,680 |
| Cedar County | 69 | -1.57% | 18,193 | 18,483 |
| Ringgold County | 70 | -1.57% | 4,570 | 4,643 |
| Wright County | 71 | -1.62% | 12,714 | 12,923 |
| Appanoose County | 72 | -1.63% | 12,083 | 12,283 |
| Winneshiek County | 73 | -1.66% | 19,718 | 20,051 |
| Butler County | 74 | -1.72% | 14,087 | 14,334 |
| Worth County | 75 | -1.86% | 7,292 | 7,430 |
| Fayette County | 76 | -1.97% | 19,065 | 19,448 |
| Chickasaw County | 77 | -2.01% | 11,744 | 11,985 |
| Palo Alto County | 78 | -2.02% | 8,811 | 8,993 |
| Tama County | 79 | -2.08% | 16,689 | 17,044 |
| Carroll County | 80 | -2.08% | 20,302 | 20,734 |
| Taylor County | 81 | -2.18% | 5,733 | 5,861 |
| Osceola County | 82 | -2.32% | 6,056 | 6,200 |
| Keokuk County | 83 | -2.49% | 9,763 | 10,012 |
| Hardin County | 84 | -2.5% | 16,405 | 16,826 |
| Kossuth County | 85 | -2.6% | 14,406 | 14,791 |
| Decatur County | 86 | -2.61% | 7,531 | 7,733 |
| Calhoun County | 87 | -2.66% | 9,632 | 9,895 |
| Muscatine County | 88 | -2.8% | 41,948 | 43,155 |
| Emmet County | 89 | -3.16% | 9,047 | 9,342 |
| Clarke County | 90 | -3.22% | 9,417 | 9,730 |
| Montgomery County | 91 | -3.41% | 9,978 | 10,330 |
| Ida County | 92 | -3.47% | 6,785 | 7,029 |
| Lee County | 93 | -3.84% | 32,243 | 33,529 |
| Sac County | 94 | -4.05% | 9,403 | 9,800 |
| Winnebago County | 95 | -4.25% | 10,203 | 10,656 |
| Monroe County | 96 | -4.42% | 7,260 | 7,596 |
| Monona County | 97 | -4.43% | 8,355 | 8,742 |
| Floyd County | 98 | -5.41% | 14,750 | 15,593 |
| Henry County | 99 | -6.35% | 19,149 | 20,447 |
Iowa's counties show varied growth patterns from 2020 to 2025. Dallas County leads with 18.45% annualized growth, followed by Warren County (9.12%) and Polk County (6.46%). The largest counties are Polk County (524,883), Linn County (234,122), and Scott County (176,613). Of the 99 counties in Iowa, 46 are growing while 53 have experienced population decline. Overall, counties averaged -0.06% annualized growth, with total population growing by 2.3% annually.
-0.05
-0.025
0
0.025
0.05
0.075