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List of Counties in Illinois

Discover Illinois’s population facts easily with our list of counties and cities. Find out how many people live in each area, from big cities to small towns, and see how Illinois’s population is spread out across the state.

A county is an administrative subdivision of a US state or territory. As of 2022, Illinois is divided into 102 counties. 

Cook County is the most populated county in Illinois home to Chicago and the second-most populous county in the United States. Hardin County is the Least populated. The largest county by land area is McLean County while the smallest is Putnam County. 

read about the Population of Illinois

Illinois Counties by Population

#CountyPopulation 2021Area
(sq. mi)
1Cook County5,173,146944
2DuPage County924,885327
3Lake County711,239443
4Will County697,252835
5Kane County515,588519
6McHenry County311,122603
7Winnebago County283,119513
8Madison County264,490716
9St. Clair County254,796657
10Champaign County205,943996
11Sangamon County194,734868
12Peoria County179,432618
13McLean County170,8891,183
14Rock Island County142,909427
15Kendall County134,867320
16Tazewell County130,413646
17LaSalle County108,9651,135
18Kankakee County106,601676
19Macon County102,432580
20DeKalb County100,414631
21Vermilion County73,095898
22Williamson County66,879420
23Adams County64,954855
24Whiteside County55,305684
25Boone County53,159280
26Grundy County52,989418
27Jackson County52,565584
28Ogle County51,449758
29Knox County49,268716
30Henry County48,907822
31Coles County46,765508
32Macoupin County44,406862
33Stephenson County44,021564
34Woodford County38,225527
35Franklin County37,442408
36Marion County37,390572
37Jefferson County36,877571
38Clinton County36,793474
39Livingston County35,6641,043
40Monroe County34,932385
41Effingham County34,430478
42Lee County34,049724
43Christian County33,662709
44Fulton County33,197865
45Bureau County32,883869
46Morgan County32,606568
47Randolph County30,142575
48Montgomery County28,084703
49Logan County27,992618
50McDonough County26,828589
51Iroquois County26,8271,117
52Saline County23,320379
53Jo Daviess County21,939600
54Fayette County21,384716
55Jersey County21,333369
56Perry County20,985441
57Shelby County20,789758
58Douglas County19,722416
59Crawford County18,659443
60Hancock County17,400793
61Union County16,923413
62Piatt County16,753439
63Bond County16,596380
64Warren County16,531542
65Edgar County16,520623
66Wayne County15,963713
67Richland County15,796360
68Carroll County15,698445
69Mercer County15,582561
70DeWitt County15,341397
71Clark County15,300501
72Lawrence County15,152372
73Pike County14,618831
74Moultrie County14,510335
75Massac County13,960237
76White County13,784494
77Washington County13,655562
78Ford County13,511485
79Johnson County13,463343
80Clay County13,143468
81Mason County12,881539
82Cass County12,773375
83Menard County12,164314
84Greene County11,843543
85Marshall County11,663386
86Wabash County11,202223
87Cumberland County10,345345
88Jasper County9,193494
89Hamilton County7,911434
90Schuyler County6,843437
91Brown County6,421305
92Henderson County6,312378
93Edwards County6,075222
94Putnam County5,566160
95Stark County5,294288
96Pulaski County5,065199
97Alexander County5,030236
98Gallatin County4,903322
99Scott County4,836250
100Calhoun County4,369253
101Pope County3,779368
102Hardin County3,650177

Source: US Census report 2021

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Most Populous Counties in Illinois

The most populous county in Illinois is  Cook County with 5 million residents. It’s the second most populous county in the United States just behind Los Angeles County. It is followed by DuPage County (1 million) and Lake County (0.7 million)

Let’s have a look at the Top 10 most populous counties

#CountyPopulation 2021
1Cook County5,173,146
2DuPage County924,885
3Lake County711,239
4Will County697,252
5Kane County515,588
6McHenry County311,122
7Winnebago County283,119
8Madison County264,490
9St. Clair County254,796
10Champaign County205,943
Least Populated California County

The least populous county is Hardin County with 3,650 residents. it’s followed by Pope and Calhoun County with populations of 3,779 and 4,369 people respectively.

Let’s have a look at 5 least populated counties in Illinois

#CountyPopulation 2021
1Hardin County3,650
2Pope County3,779
3Calhoun County4,369
4Scott County4,836
5Gallatin County4,903

source: US Census 2021

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Largest counties in Illinois by area

The Largest county by Land Area in Illinois is McLean County with an area of 1,183 sq. miles. Next is LaSalle with an area of 1,135 sq. mi. followed by Iroquois County (1,117  sq. mi.)

Let’s have a look at the Top 10 counties by Area

#CountyArea (sq. mi)
1McLean County1,183
2LaSalle County1,135
3Iroquois County1,117
4Livingston County1,043
5Champaign County996
6Cook County944
7Vermilion County898
8Bureau County869
9Sangamon County868
10Fulton County865
Smallest County in Illinois by area

The smallest county by area in Illinois is Putnam County with an area of 160 square miles.

#CountyArea (sq. mi)
1Putnam County160
2Hardin County177
3Pulaski County199
4Edwards County222
5Wabash County223


Most densely populated Counties in Illinois

The most densely populated county in Illinois is Cook County, with 5,480 people per sq. mi. Next comes DuPage County with 2828 people per sq. mi followed by Lake County (1605/ sq.mi)

Let’s have a look at the Top 10 densely populated counties

#CountyDensity (people/ sq mi.)
1Cook County5,480.03
2DuPage County2,828.39
3Lake County1,605.51
4Kane County993.43
5Will County835.03
6Winnebago County551.89
7McHenry County515.96
8Kendall County421.46
9St. Clair County387.82
10Madison County369.40
Least Densely Populated County in Illinois 
#CountyDensity (people/ sq mi.)
1Pope County10.27
2Gallatin County15.23
3Schuyler County15.66
4Henderson County16.70
5Calhoun County17.27
6Pike County17.59

source: US Census 2021

Top Cities in Illinois

Illinois is divided into 102 counties and, as of 2020, contained 1,300 municipalities consisting of cities, towns, and villages. The largest city bady population is Chicago with 2,746,388 residents followed by Aurora, Joilet, Naperville,  and Rockford. The largest city by land area is Chicago, which spans 227.73 sq mi (589.8 km2) 

read about Top cities in Illinois by population

List of Counties in Illinois by population 2024