Largest Counties in Iowa

Rank County Population County Seat Established Area (km2) Density
1 Polk County 430,629 Des Moines 1846 1,476 291.75
2 Linn County 211,215 Cedar Rapids 1837 1,860 113.56
3 Scott County 165,213 Davenport 1837 1,186 139.3
4 Black Hawk County 131,079 Waterloo 1843 1,469 89.23
5 Johnson County 130,871 Iowa City 1837 1,590 82.31
6 Woodbury County 102,161 Sioux City 1853 2,261 45.18
7 Dubuque County 93,642 Dubuque 1834 1,575 59.46
8 Pottawattamie County 93,147 Council Bluffs 1847 2,471 37.7
9 Story County 89,531 Nevada 1846 1,484 60.33
10 Dallas County 66,124 Adel 1846 1,518 43.56
11 Clinton County 49,105 Clinton 1837 1,800 27.28
12 Warren County 46,214 Indianola 1846 1,481 31.2
13 Cerro Gordo County 44,140 Mason City 1851 1,471 30.01
14 Muscatine County 42,734 Muscatine 1836 1,137 37.58
15 Marshall County 40,637 Marshalltown 1846 1,481 27.44
16 Des Moines County 40,314 Burlington 1834 1,077 37.43
17 Webster County 38,002 Fort Dodge 1853 1,852 20.52
18 Jasper County 36,831 Newton 1846 1,891 19.48
19 Lee County 35,851 Fort Madison 1836 1,339 26.77
20 Wapello County 35,614 Ottumwa 1843 1,119 31.83
21 Sioux County 33,693 Orange City 1851 1,989 16.94
22 Marion County 33,298 Knoxville 1845 1,435 23.2
23 Boone County 26,295 Boone 1846 1,481 17.75
24 Benton County 26,065 Vinton 1837 1,854 14.06
25 Plymouth County 24,975 Le Mars 1851 2,238 11.16
26 Bremer County 24,265 Waverly 1851 1,109 21.88
27 Mahaska County 22,370 Oskaloosa 1843 1,479 15.13
28 Washington County 21,693 Washington 1839 1,474 14.72
29 Winneshiek County 21,045 Decorah 1847 1,787 11.78
30 Buchanan County 20,947 Independence 1837 1,479 14.16
31 Fayette County 20,869 West Union 1837 1,893 11.02
32 Carroll County 20,805 Carroll 1851 1,474 14.11
33 Jones County 20,627 Anamosa 1837 1,489 13.85
34 Buena Vista County 20,249 Storm Lake 1851 1,489 13.6
35 Henry County 20,134 Mount Pleasant 1836 1,124 17.91
36 Jackson County 19,837 Maquoketa 1837 1,647 12.04
37 Poweshiek County 18,903 Montezuma 1843 1,515 12.48
38 Cedar County 18,488 Tipton 1837 1,502 12.31
39 Clayton County 18,118 Elkader 1837 2,018 8.98
40 Tama County 17,756 Toledo 1843 1,867 9.51
41 Delaware County 17,753 Manchester 1837 1,497 11.86
42 Hardin County 17,523 Eldora 1851 1,474 11.89
43 Crawford County 17,085 Denison 1851 1,849 9.24
44 Jefferson County 16,832 Fairfield 1839 1,127 14.94
45 Clay County 16,656 Spencer 1851 1,474 11.3
46 Dickinson County 16,656 Spirit Lake 1851 987 16.88
47 Iowa County 16,344 Marengo 1843 1,518 10.77
48 Floyd County 16,292 Charles City 1851 1,298 12.55
49 Page County 15,921 Clarinda 1847 1,386 11.49
50 Madison County 15,668 Winterset 1846 1,453 10.78
51 Hamilton County 15,662 Webster City 1856 1,494 10.48
52 Kossuth County 15,532 Algona 1851 2,520 6.16
53 Mills County 15,048 Glenwood 1851 1,132 13.29
54 Harrison County 14,917 Logan 1851 1,805 8.26
55 Butler County 14,856 Allison 1851 1,502 9.89
56 O’Brien County 14,387 Primghar 1851 1,484 9.69
57 Allamakee County 14,319 Waukon 1847 1,658 8.64
58 Cass County 13,945 Atlantic 1851 1,461 9.54
59 Wright County 13,218 Clarion 1851 1,505 8.78
60 Appanoose County 12,873 Centerville 1843 1,285 10.02
61 Union County 12,523 Creston 1851 1,098 11.41
62 Grundy County 12,442 Grundy Center 1851 1,303 9.55
63 Chickasaw County 12,428 New Hampton 1851 1,308 9.5
64 Shelby County 12,156 Harlan 1851 1,531 7.94
65 Cherokee County 12,061 Cherokee 1851 1,494 8.07
66 Lyon County 11,570 Rock Rapids 1851 1,523 7.6
67 Louisa County 11,376 Wapello 1836 1,041 10.93
68 Hancock County 11,330 Garner 1851 1,479 7.66
69 Guthrie County 10,943 Guthrie Center 1851 1,531 7.15
70 Winnebago County 10,855 Forest City 1851 1,036 10.48
71 Mitchell County 10,765 Osage 1851 1,215 8.86
72 Montgomery County 10,729 Red Oak 1851 1,098 9.77
73 Franklin County 10,669 Hampton 1851 1,507 7.08
74 Keokuk County 10,500 Sigourney 1837 1,500 7
75 Sac County 10,339 Sac City 1851 1,492 6.93
76 Emmet County 10,291 Estherville 1851 1,026 10.03
77 Humboldt County 9,804 Dakota City 1857 1,124 8.72
78 Calhoun County 9,659 Rockwell City 1851 1,476 6.54
79 Howard County 9,555 Cresco 1851 1,225 7.8
80 Palo Alto County 9,410 Emmetsburg 1851 1,461 6.44
81 Greene County 9,325 Jefferson 1851 1,471 6.34
82 Clarke County 9,275 Osceola 1846 1,116 8.31
83 Monona County 9,232 Onawa 1851 1,795 5.14
84 Lucas County 8,887 Chariton 1846 1,116 7.96
85 Davis County 8,742 Bloomfield 1843 1,303 6.71
86 Decatur County 8,446 Leon 1846 1,378 6.13
87 Monroe County 7,959 Albia 1843 1,121 7.1
88 Adair County 7,671 Greenfield 1851 1,474 5.2
89 Worth County 7,587 Northwood 1851 1,036 7.32
90 Van Buren County 7,559 Keosauqua 1836 1,256 6.02
91 Fremont County 7,430 Sidney 1847 1,323 5.62
92 Pocahontas County 7,299 Pocahontas 1851 1,497 4.88
93 Ida County 7,078 Ida Grove 1851 1,119 6.33
94 Osceola County 6,451 Sibley 1851 1,033 6.24
95 Wayne County 6,392 Corydon 1846 1,362 4.69
96 Taylor County 6,306 Bedford 1847 1,383 4.56
97 Audubon County 6,108 Audubon 1851 1,147 5.33
98 Ringgold County 5,120 Mount Ayr 1847 1,393 3.68
99 Adams County 4,018 Corning 1851 1,098 3.66

Largest Counties in Iowa

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