Data / Rankings / Population density / Counties in Illinois

Counties in Illinois by population density, 2025

Cook County had the highest population density of 102 counties in 2025, at 2,122.5 inhabitants per km². Pope County had the lowest, at 3.8 inhabitants per km². The median was 17.1 inhabitants per km² and the figure for Illinois was 88.5 inhabitants per km². Source: the U.S. Census Bureau.

Highest2,122.5Cook County
Lowest3.8Pope County
Median17.1102 counties
Illinois88.5History

Top 40 counties, 2025

CSVChart (SVG)

Cook CountyCook County: 2,122.5 inhabitants per km²2,122.5DuPage CountyDuPage County: 1,100.1 inhabitants per km²1,100.1Lake CountyLake County: 626 inhabitants per km²626Kane CountyKane County: 390.9 inhabitants per km²390.9Will CountyWill County: 329 inhabitants per km²329Winnebago CountyWinnebago County: 213.5 inhabitants per km²213.5McHenry CountyMcHenry County: 203.3 inhabitants per km²203.3Kendall CountyKendall County: 175.4 inhabitants per km²175.4St. Clair CountySt. Clair County: 147.2 inhabitants per km²147.2Madison CountyMadison County: 142 inhabitants per km²142Rock Island CountyRock Island County: 128.1 inhabitants per km²128.1Peoria CountyPeoria County: 111.4 inhabitants per km²111.4Sangamon CountySangamon County: 86.3 inhabitants per km²86.3Champaign CountyChampaign County: 81.4 inhabitants per km²81.4Tazewell CountyTazewell County: 77.7 inhabitants per km²77.7Boone CountyBoone County: 73.7 inhabitants per km²73.7Macon CountyMacon County: 66 inhabitants per km²66DeKalb CountyDeKalb County: 62.3 inhabitants per km²62.3Williamson CountyWilliamson County: 61.8 inhabitants per km²61.8Kankakee CountyKankakee County: 60.2 inhabitants per km²60.2McLean CountyMcLean County: 55.9 inhabitants per km²55.9Grundy CountyGrundy County: 49.9 inhabitants per km²49.9LaSalle CountyLaSalle County: 36.7 inhabitants per km²36.7Coles CountyColes County: 35.4 inhabitants per km²35.4Monroe CountyMonroe County: 34.9 inhabitants per km²34.9Franklin CountyFranklin County: 34.9 inhabitants per km²34.9Jackson CountyJackson County: 34.7 inhabitants per km²34.7Vermilion CountyVermilion County: 30.6 inhabitants per km²30.6Whiteside CountyWhiteside County: 30.5 inhabitants per km²30.5Clinton CountyClinton County: 30.2 inhabitants per km²30.2Stephenson CountyStephenson County: 29.6 inhabitants per km²29.6Adams CountyAdams County: 29 inhabitants per km²29Woodford CountyWoodford County: 27.9 inhabitants per km²27.9Effingham CountyEffingham County: 27.8 inhabitants per km²27.8Ogle CountyOgle County: 26.2 inhabitants per km²26.2Knox CountyKnox County: 25.7 inhabitants per km²25.7Marion CountyMarion County: 24.5 inhabitants per km²24.5Jefferson CountyJefferson County: 24.4 inhabitants per km²24.4Saline CountySaline County: 23.1 inhabitants per km²23.1Henry CountyHenry County: 22.6 inhabitants per km²22.6
inhabitants per km². Source: Invokely calculation with data from U.S. Census Bureau. Retrieved 2026-10-09.

Full ranking

RankCounties2025
inhabitants per km²		Change on 2024
1Cook County2,122.5+0.1%
2DuPage County1,100.1+0.2%
3Lake County626+0.1%
4Kane County390.9+0.4%
5Will County329+0.5%
6Winnebago County213.5+0.3%
7McHenry County203.3+0.6%
8Kendall County175.4+1.6%
9St. Clair County147.2-0.3%
10Madison County142-0.1%
11Rock Island County128.1+0.2%
12Peoria County111.40%
13Sangamon County86.3+0.1%
14Champaign County81.4+0.4%
15Tazewell County77.7+0.1%
16Boone County73.7+0.1%
17Macon County66-0.6%
18DeKalb County62.3+1.2%
19Williamson County61.8+0.2%
20Kankakee County60.2-0.3%
21McLean County55.9-0.1%
22Grundy County49.9+0.6%
23LaSalle County36.7-0.1%
24Coles County35.4+0.1%
25Monroe County34.9-0.8%
26Franklin County34.9-0.1%
27Jackson County34.7-0.3%
28Vermilion County30.6-0.3%
29Whiteside County30.5-0.6%
30Clinton County30.2+0.1%
31Stephenson County29.6-0.5%
32Adams County29+0.1%
33Woodford County27.9-0.2%
34Effingham County27.8-0.1%
35Ogle County26.2+0.2%
36Knox County25.7-0.4%
37Marion County24.5-0.3%
38Jefferson County24.4+0.1%
39Saline County23.1-0.3%
40Henry County22.6-0.2%
41Jersey County22.10%
42Morgan County22.1-0.4%
43Massac County22-0.8%
44Randolph County20.1+0.2%
45Macoupin County19.6-0.4%
46Wabash County18.9-1.1%
47Douglas County18.4+0.2%
48Christian County18.20%
49Perry County17.6-1.1%
50Lee County17.5+0.2%
51Bond County17.2+2.2%
52Logan County17-0.1%
53McDonough County17-0.8%
54Moultrie County16.5-0.5%
55Richland County16.3-1%
56Crawford County16.2+0.1%
57Union County15.6-1%
58Montgomery County15.4+0.9%
59Johnson County15+0.1%
60Piatt County14.8+0.9%
61De Witt County14.7-0.8%
62Fulton County14.7+0.3%
63Menard County14.6-0.5%
64Bureau County14.4-0%
65Lawrence County14.3+0.2%
66Jo Daviess County13.9-0.3%
67Putnam County13.60%
68Carroll County13.4-0.3%
69Livingston County13-0.4%
70Cass County12.8-0.5%
71Clark County11.6-0.2%
72Warren County11.5+0.7%
73Marshall County11.5-0.8%
74Cumberland County11.4-0.7%
75Fayette County11.2-0.8%
76Clay County10.5-0.4%
77Ford County10.5-0.8%
78Mercer County10.5-0.4%
79Shelby County10.5+0.1%
80White County10.3-1.5%
81Edwards County10.2-1.5%
82Edgar County10.1-0.4%
83Pulaski County9.3-1.3%
84Washington County9.3-0.1%
85Iroquois County9-0.3%
86Mason County8.9-0.6%
87Wayne County8.6-0%
88Hancock County8.2-0.8%
89Brown County8.1-0.6%
90Greene County8-0.7%
91Hardin County7.8-0.4%
92Alexander County7.5-0.9%
93Scott County7.5-0.5%
94Stark County7.1+0.9%
95Jasper County7.1-0.2%
96Hamilton County7-0%
97Pike County6.6-0.4%
98Calhoun County6.5-0.2%
99Henderson County6.1-0.8%
100Schuyler County5.9-1%
101Gallatin County5.5-1.4%
102Pope County3.8-1.2%

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.

Use this data in your AI agent

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Rank Counties in Illinois by population density using official data, and cite the source.
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Questions

Which county has the highest population density?

Cook County, with 2,122.5 inhabitants per km² in 2025, according to the U.S. Census Bureau.

Which county has the lowest population density?

Pope County, with 3.8 inhabitants per km² in 2025.

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 Illinois: more rankings