Data / Rankings / Population density / Counties in Iowa

Counties in Iowa by population density

Polk County had the highest population density of 99 counties in 2021, at 335.7 inhabitants per km². Adams County had the lowest, at 3.3 inhabitants per km². The median was 10.3 inhabitants per km² and the figure for Iowa was 22.1 inhabitants per km². Source: the U.S. Census Bureau.

Highest335.7Polk County
Lowest3.3Adams County
Median10.399 counties
Iowa22.1History

Top 40 counties, 2021

CSVChart (SVG)

Polk CountyPolk County: 335.7 inhabitants per km²335.7Scott CountyScott County: 146.9 inhabitants per km²146.9Linn CountyLinn County: 123.6 inhabitants per km²123.6Johnson CountyJohnson County: 97.7 inhabitants per km²97.7Black Hawk CountyBlack Hawk County: 89.1 inhabitants per km²89.1Dallas CountyDallas County: 68.4 inhabitants per km²68.4Story CountyStory County: 67.2 inhabitants per km²67.2Dubuque CountyDubuque County: 62.8 inhabitants per km²62.8Woodbury CountyWoodbury County: 46.8 inhabitants per km²46.8Pottawattamie CountyPottawattamie County: 37.9 inhabitants per km²37.9Muscatine CountyMuscatine County: 37.7 inhabitants per km²37.7Warren CountyWarren County: 36.3 inhabitants per km²36.3Des Moines CountyDes Moines County: 35.8 inhabitants per km²35.8Wapello CountyWapello County: 31.6 inhabitants per km²31.6Cerro Gordo CountyCerro Gordo County: 29.1 inhabitants per km²29.1Marshall CountyMarshall County: 26.9 inhabitants per km²26.9Clinton CountyClinton County: 25.8 inhabitants per km²25.8Lee CountyLee County: 24.8 inhabitants per km²24.8Marion CountyMarion County: 23.3 inhabitants per km²23.3Bremer CountyBremer County: 22.3 inhabitants per km²22.3Webster CountyWebster County: 20.1 inhabitants per km²20.1Jasper CountyJasper County: 20 inhabitants per km²20Dickinson CountyDickinson County: 18.1 inhabitants per km²18.1Henry CountyHenry County: 18.1 inhabitants per km²18.1Boone CountyBoone County: 18.1 inhabitants per km²18.1Sioux CountySioux County: 18.1 inhabitants per km²18.1Washington CountyWashington County: 15.3 inhabitants per km²15.3Mahaska CountyMahaska County: 14.9 inhabitants per km²14.9Carroll CountyCarroll County: 14.1 inhabitants per km²14.1Buchanan CountyBuchanan County: 14 inhabitants per km²14Jefferson CountyJefferson County: 14 inhabitants per km²14Jones CountyJones County: 14 inhabitants per km²14Buena Vista CountyBuena Vista County: 14 inhabitants per km²14Benton CountyBenton County: 13.9 inhabitants per km²13.9Mills CountyMills County: 12.8 inhabitants per km²12.8Poweshiek CountyPoweshiek County: 12.3 inhabitants per km²12.3Cedar CountyCedar County: 12.3 inhabitants per km²12.3Floyd CountyFloyd County: 11.9 inhabitants per km²11.9Jackson CountyJackson County: 11.8 inhabitants per km²11.8Delaware CountyDelaware County: 11.7 inhabitants per km²11.7
inhabitants per km². Source: Invokely calculation with data from U.S. Census Bureau. Retrieved 2026-10-09.

Full ranking

RankCounties2021
inhabitants per km²		Change on 2020
1Polk County335.7+1%
2Scott County146.9-0.2%
3Linn County123.6-0.4%
4Johnson County97.7+1.4%
5Black Hawk County89.1-0.4%
6Dallas County68.4+3.6%
7Story County67.2+1%
8Dubuque County62.8-0.4%
9Woodbury County46.8-0.1%
10Pottawattamie County37.9-0.3%
11Muscatine County37.7-1%
12Warren County36.3+1.7%
13Des Moines County35.8-0.8%
14Wapello County31.6-0.1%
15Cerro Gordo County29.1-0.6%
16Marshall County26.9-0.4%
17Clinton County25.8+0.1%
18Lee County24.8-0.8%
19Marion County23.3+0.1%
20Bremer County22.3+0.5%
21Webster County20.1+0.5%
22Jasper County20+0.2%
23Dickinson County18.1+0.6%
24Henry County18.1-0.2%
25Boone County18.1+0.3%
26Sioux County18.1+0.2%
27Washington County15.3-0.1%
28Mahaska County14.9-0.8%
29Carroll County14.1+0.1%
30Buchanan County14+0.5%
31Jefferson County14+0.7%
32Jones County14+0.9%
33Buena Vista County14-0%
34Benton County13.9+0.8%
35Mills County12.8+0.5%
36Poweshiek County12.3-0.1%
37Cedar County12.3-0.3%
38Floyd County11.9-0.8%
39Jackson County11.8-0.3%
40Delaware County11.7+0.6%
41Madison County11.6+1%
42Plymouth County11.5+0.2%
43Hardin County11.3-0.6%
44Clay County11.2+0.8%
45Winneshiek County11.2-0.5%
46Page County11+0.2%
47Union County11-0.7%
48Iowa County10.9-0.4%
49Louisa County10.3-0.8%
50Winnebago County10.3-0%
51Fayette County10.2-0.7%
52Hamilton County10-0.9%
53Butler County9.6+0.1%
54Appanoose County9.5-0.1%
55Grundy County9.5+0.2%
56O'Brien County9.5-0.7%
57Montgomery County9.4-0.1%
58Chickasaw County9.1-0.8%
59Emmet County9.1-0.1%
60Tama County9-1%
61Cass County9-0.2%
62Crawford County8.8-1.5%
63Clarke County8.7+0.2%
64Mitchell County8.7-0.3%
65Humboldt County8.6+0.4%
66Wright County8.5-0.8%
67Clayton County8.5+0.2%
68Allamakee County8.4-0.7%
69Harrison County8.1+0.8%
70Lyon County7.9+0.9%
71Lucas County7.8+1.1%
72Howard County7.8+0.1%
73Cherokee County7.7-1%
74Shelby County7.7+0.4%
75Hancock County7.2-0.7%
76Worth County7.1-0.7%
77Davis County7+0.4%
78Guthrie County6.9-0.2%
79Monroe County6.8-0.1%
80Calhoun County6.70%
81Keokuk County6.6-1%
82Franklin County6.6-0.4%
83Sac County6.6-0.3%
84Ida County6.2-0.8%
85Palo Alto County6.1-0.6%
86Osceola County6-0.4%
87Greene County5.9-0.2%
88Van Buren County5.8+0.5%
89Kossuth County5.8-1.9%
90Decatur County5.7+0.9%
91Adair County5.1+0.4%
92Fremont County5+0.3%
93Audubon County4.9-0.7%
94Wayne County4.8+0.3%
95Monona County4.8-1.6%
96Pocahontas County4.7-0.4%
97Taylor County4.3+0.1%
98Ringgold County3.3-0.2%
99Adams County3.3-1.9%

Other periods

About this ranking

Resident population divided by land area in km². World Bank figures use mid-year population and land area excluding inland water.

United States: Census Bureau population estimates for 1 July divided by land area (water excluded) from the latest Census Gazetteer files. US tables often give people per square mile; multiply persons per km² by 2.59 to compare.

Every value in the ranking comes from the same publisher and the same period, so the counties are compared on one definition. Equal values share a rank.

How to cite

U.S. Census Bureau. Population Estimates Program resident population on 1 July divided by land area from the latest Census Gazetteer files, persons per km². https://www2.census.gov/programs-surveys/popest/datasets/2020-2025/. Retrieved 2026-10-09.

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Questions

Which county has the highest population density?

Polk County, with 335.7 inhabitants per km² in 2021, according to the U.S. Census Bureau.

Which county has the lowest population density?

Adams County, with 3.3 inhabitants per km² in 2021.

Where does this ranking come from?

Every value comes from one source and one period, so the places are comparable: U.S. Census Bureau, Population Estimates Program resident population on 1 July divided by land area from the latest Census Gazetteer files, persons per km². Retrieved 2026-10-09.

Population density: other rankings

Counties in Iowa: more rankings