RANKING · 2025 ESTIMATES · 99 SHOWN OF 99

Largest by population, Iowa counties

The most populous Iowa counties as of the 2025 population estimates. This list covers the 99 counties in Iowa that qualify, ranked against each other statewide. The median across all 99 is 14,901.

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SAME RANKING BYCities States Metros ZIP codes

RELATEDFastest growing Fastest shrinking Most population gained Most population lost Most densely populated Most sparsely populated

YEAR1990 2000 2010 2020 2025

RANKPLACESTATETOTAL POPULATIONVS 2000

01Polk County, IAIA516,546+38%

02Linn County, IAIA232,028+21%

03Scott County, IAIA175,259+10%

04Johnson County, IAIA160,044+44%

05Black Hawk County, IAIA131,532+3%

06▲1Dallas County, IAIA118,457+191%

07▼1Woodbury County, IAIA106,649+3%

08▲1Story County, IAIA101,291+27%

09▼1Dubuque County, IAIA99,381+11%

10Pottawattamie County, IAIA92,996+6%

11Warren County, IAIA57,331+41%

12Clinton County, IAIA46,002−8%

13▲1Cerro Gordo County, IAIA42,372−9%

14▼1Muscatine County, IAIA41,8530%

15Marshall County, IAIA39,890+1%

16▲1Jasper County, IAIA38,153+3%

17▼1Des Moines County, IAIA38,077−10%

18Webster County, IAIA36,838−8%

19Sioux County, IAIA36,774+16%

20Wapello County, IAIA35,210−2%

21▲1Marion County, IAIA34,192+7%

22▼1Lee County, IAIA32,306−15%

23Boone County, IAIA26,799+2%

24▲1Benton County, IAIA26,004+3%

25▼1Plymouth County, IAIA25,697+3%

26Bremer County, IAIA25,296+8%

27Washington County, IAIA22,667+10%

28Mahaska County, IAIA21,880−2%

29▲2Jones County, IAIA21,253+5%

30▲2Buchanan County, IAIA20,883−1%

31▼2Buena Vista County, IAIA20,4490%

32▼2Carroll County, IAIA20,303−5%

33▲1Winneshiek County, IAIA19,733−7%

34▼1Henry County, IAIA19,349−5%

35▲1Jackson County, IAIA19,288−5%

36▼1Fayette County, IAIA19,047−13%

37Poweshiek County, IAIA18,368−2%

38Cedar County, IAIA18,359+1%

39Dickinson County, IAIA18,077+10%

40Delaware County, IAIA17,674−4%

41▲4Madison County, IAIA17,270+23%

42Clayton County, IAIA16,845−10%

43▼2Tama County, IAIA16,796−7%

44Iowa County, IAIA16,504+5%

45▼2Hardin County, IAIA16,455−13%

46Crawford County, IAIA16,237−4%

47Clay County, IAIA16,202−7%

48Jefferson County, IAIA15,291−6%

49▲2Hamilton County, IAIA14,944−9%

50▼1Floyd County, IAIA14,901−12%

51▼1Page County, IAIA14,856−12%

52▲2Mills County, IAIA14,793+2%

53Harrison County, IAIA14,623−7%

54▼2Kossuth County, IAIA14,322−17%

55▲2Allamakee County, IAIA14,238−3%

56O'Brien County, IAIA14,220−6%

57▼2Butler County, IAIA14,049−8%

58Cass County, IAIA12,960−12%

59Wright County, IAIA12,801−11%

60Grundy County, IAIA12,3610%

61▲3Lyon County, IAIA12,354+5%

62▼1Appanoose County, IAIA12,077−12%

63▼1Union County, IAIA11,829−4%

64▲1Shelby County, IAIA11,689−11%

65▼2Chickasaw County, IAIA11,663−11%

66Cherokee County, IAIA11,369−13%

67▲3Guthrie County, IAIA10,782−5%

68▲3Mitchell County, IAIA10,650−2%

69▼1Hancock County, IAIA10,528−13%

70▼3Louisa County, IAIA10,416−15%

71▼2Winnebago County, IAIA10,251−13%

72Montgomery County, IAIA10,002−15%

73▲1Franklin County, IAIA9,868−8%

74▼1Keokuk County, IAIA9,797−14%

75▲2Clarke County, IAIA9,574+5%

76▼1Calhoun County, IAIA9,562−14%

77▼1Sac County, IAIA9,525−17%

78▲1Howard County, IAIA9,415−5%

79▼1Humboldt County, IAIA9,409−9%

80▲1Davis County, IAIA9,230+8%

81▼1Emmet County, IAIA9,107−17%

82Palo Alto County, IAIA8,899−12%

83▲2Lucas County, IAIA8,847−6%

84▼1Greene County, IAIA8,658−16%

85▼1Monona County, IAIA8,539−15%

86Decatur County, IAIA7,655−12%

87Monroe County, IAIA7,406−8%

88Adair County, IAIA7,403−10%

89Worth County, IAIA7,338−7%

90Van Buren County, IAIA7,131−9%

91Pocahontas County, IAIA6,819−21%

92Ida County, IAIA6,777−14%

93▲1Wayne County, IAIA6,7380%

94▼1Fremont County, IAIA6,522−19%

95Osceola County, IAIA5,980−15%

96Taylor County, IAIA5,835−16%

97Audubon County, IAIA5,509−19%

98Ringgold County, IAIA4,642−15%

99Adams County, IAIA3,617−19%

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UPDATED 2026-09-11 · DATA: US CENSUS BUREAU POPULATION ESTIMATES