Illinois

Demographics   Counties   Cities   ZIP Codes
By alphabetical   By population   Richest   Poorest
Main / Illinois / Counties / By population

Illinois counties by population

Number of counties: 102
Population: 12,821,813
Largest county: Cook County
Table of counties in Illinois sorted by population from largest to smallest.
CountyPopulation
Cook County5,265,398
DuPage County934,094
Lake County714,484
Will County696,403
Kane County518,648
McHenry County310,749
Winnebago County285,471
Madison County266,112
St. Clair County258,597
Champaign County206,583
Sangamon County196,759
Peoria County182,439
McLean County171,455
Rock Island County144,694
Tazewell County131,977
Kendall County130,757
LaSalle County109,986
Kankakee County108,104
Macon County104,331
DeKalb County100,922
Vermilion County74,953
Williamson County67,271
Adams County65,878
Whiteside County55,932
Jackson County53,676
Boone County53,592
Grundy County52,364
Ogle County51,787
Knox County50,193
Henry County49,412
Coles County47,542
Macoupin County45,152
Stephenson County44,817
Woodford County38,571
Franklin County38,068
Marion County37,781
Jefferson County37,362
Clinton County37,048
Livingston County35,902
Monroe County34,732
Effingham County34,576
Lee County34,373
Christian County34,038
Fulton County34,022
Bureau County33,338
Morgan County33,189
Randolph County30,632
Montgomery County28,482
Logan County28,238
McDonough County27,743
Iroquois County27,362
Saline County23,869
Jo Daviess County21,995
Jersey County21,533
Fayette County21,514
Shelby County21,160
Perry County21,158
Douglas County19,708
Crawford County18,825
Hancock County17,750
Union County17,259
Edgar County16,998
Warren County16,887
Bond County16,804
Piatt County16,664
Wayne County16,250
Richland County15,876
Mercer County15,779
De Witt County15,653
Clark County15,587
Carroll County15,586
Lawrence County15,465
Pike County14,923
Moultrie County14,634
Massac County14,280
White County13,959
Washington County13,827
Ford County13,589
Clay County13,313
Johnson County13,238
Mason County13,225
Cass County13,058
Menard County12,343
Greene County12,187
Marshall County11,781
Wabash County11,414
Cumberland County10,528
Jasper County9,324
Hamilton County8,021
Schuyler County6,953
Henderson County6,485
Brown County6,330
Edwards County6,233
Putnam County5,638
Alexander County5,488
Stark County5,436
Pulaski County5,279
Gallatin County5,038
Scott County4,923
Calhoun County4,537
Pope County3,820
Hardin County3,700

What is the largest county in Illinois?

Cook County is the largest county in Illinois with a population of 5,265,398.

TOP-5 counties by population in Illinois:
  • Cook County
  • DuPage County
  • Lake County
  • Will County
  • Kane County