RANKING · 2020 CENSUS · 99 SHOWN OF 99

Largest by population, Iowa counties · 2020

The most populous Iowa counties as of the 2020 population estimates. This list covers the 99 counties in Iowa that qualify, ranked against each other statewide.

IowaAll states All rankings

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, IAIA492,401+31%

02Linn County, IAIA230,299+20%

03Scott County, IAIA174,669+10%

04Johnson County, IAIA152,854+38%

05Black Hawk County, IAIA131,144+2%

06Woodbury County, IAIA105,941+2%

07Dallas County, IAIA99,678+145%

08Dubuque County, IAIA99,266+11%

09Story County, IAIA98,537+23%

10Pottawattamie County, IAIA93,667+7%

11Warren County, IAIA52,403+29%

12Clinton County, IAIA46,460−7%

13Muscatine County, IAIA43,235+4%

14Cerro Gordo County, IAIA43,127−7%

15Marshall County, IAIA40,105+2%

16Des Moines County, IAIA38,910−8%

17Jasper County, IAIA37,813+2%

18Webster County, IAIA36,999−8%

19Sioux County, IAIA35,872+14%

20Wapello County, IAIA35,437−2%

21Lee County, IAIA33,555−12%

22Marion County, IAIA33,414+4%

23Boone County, IAIA26,715+2%

24Plymouth County, IAIA25,698+3%

25Benton County, IAIA25,575+1%

26Bremer County, IAIA24,988+7%

27Washington County, IAIA22,565+9%

28Mahaska County, IAIA22,190−1%

29Buena Vista County, IAIA20,823+2%

30Carroll County, IAIA20,760−3%

31Jones County, IAIA20,646+2%

32Buchanan County, IAIA20,565−3%

33Henry County, IAIA20,482+1%

34Winneshiek County, IAIA20,070−6%

35Fayette County, IAIA19,509−11%

36Jackson County, IAIA19,485−4%

37Poweshiek County, IAIA18,662−1%

38Cedar County, IAIA18,505+2%

39Dickinson County, IAIA17,703+8%

40Delaware County, IAIA17,488−5%

41Tama County, IAIA17,135−5%

42Clayton County, IAIA17,043−9%

43Hardin County, IAIA16,878−10%

44Iowa County, IAIA16,662+6%

45Madison County, IAIA16,548+18%

46Crawford County, IAIA16,525−2%

47Clay County, IAIA16,384−6%

48Jefferson County, IAIA15,663−3%

49Floyd County, IAIA15,627−8%

50Page County, IAIA15,211−10%

51Hamilton County, IAIA15,039−9%

52Kossuth County, IAIA14,828−14%

53Harrison County, IAIA14,582−7%

54Mills County, IAIA14,484−0%

55Butler County, IAIA14,334−6%

56O'Brien County, IAIA14,182−6%

57Allamakee County, IAIA14,061−4%

58Cass County, IAIA13,127−11%

59Wright County, IAIA12,943−10%

60Grundy County, IAIA12,329−0%

61Appanoose County, IAIA12,317−10%

62Union County, IAIA12,138−1%

63Chickasaw County, IAIA12,012−8%

64Lyon County, IAIA11,934+1%

65Shelby County, IAIA11,746−11%

66Cherokee County, IAIA11,658−11%

67Louisa County, IAIA10,837−11%

68Hancock County, IAIA10,795−11%

69Winnebago County, IAIA10,679−9%

70Guthrie County, IAIA10,623−6%

71Mitchell County, IAIA10,565−3%

72Montgomery County, IAIA10,330−12%

73Keokuk County, IAIA10,033−12%

74Franklin County, IAIA10,019−6%

75Calhoun County, IAIA9,927−11%

76Sac County, IAIA9,814−15%

77Clarke County, IAIA9,748+7%

78Humboldt County, IAIA9,597−8%

79Howard County, IAIA9,469−5%

80Emmet County, IAIA9,388−15%

81Davis County, IAIA9,110+7%

82Palo Alto County, IAIA8,996−11%

83Greene County, IAIA8,771−15%

84Monona County, IAIA8,751−13%

85Lucas County, IAIA8,634−8%

86Decatur County, IAIA7,645−12%

87Monroe County, IAIA7,577−5%

88Adair County, IAIA7,496−9%

89Worth County, IAIA7,443−6%

90Van Buren County, IAIA7,203−8%

91Pocahontas County, IAIA7,078−18%

92Ida County, IAIA7,005−11%

93Fremont County, IAIA6,605−18%

94Wayne County, IAIA6,497−3%

95Osceola County, IAIA6,192−12%

96Taylor County, IAIA5,896−15%

97Audubon County, IAIA5,674−17%

98Ringgold County, IAIA4,663−15%

99Adams County, IAIA3,704−17%

SHOWING 1–99 OF 99

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UPDATED 2026-07-15 · DATA: US CENSUS BUREAU DECENNIAL CENSUS