Ranking of Illinois Counties By Population in 2015
Updated on June 18, 2025.
Based on the US Census Vintage data estimates, in 2015, the Population for Illinois was 12.86M. Among all Illinois counties, Cook County had the highest population (5.24M), followed by DuPage County (933.67K), and Lake County (704.69K).
The chart below shows the top 10 counties, and the table below shows the ranking of all Illinois counties.
You can see similar ranking information for related topics, and for other states. You can also see the ranking of all counties in the United States.
Related Topics: Illinois Census Vintage Data Topic List.
Data Source: US Census Bureau (Vintage), 2015 Census.
See this for other years:
Ranking of Illinois Counties By Population in 2015
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| Rank | County | Population |
|---|---|---|
| 1 | Cook County | 5243371 |
| 2 | DuPage County | 933669 |
| 3 | Lake County | 704687 |
| 4 | Will County | 685825 |
| 5 | Kane County | 528562 |
| 6 | McHenry County | 307595 |
| 7 | Winnebago County | 287237 |
| 8 | Madison County | 266112 |
| 9 | St. Clair County | 265008 |
| 10 | Champaign County | 209534 |
| 11 | Sangamon County | 198973 |
| 12 | Peoria County | 186552 |
| 13 | McLean County | 173222 |
| 14 | Rock Island County | 146161 |
| 15 | Tazewell County | 134350 |
| 16 | Kendall County | 122892 |
| 17 | Kankakee County | 111786 |
| 18 | LaSalle County | 111015 |
| 19 | Macon County | 107398 |
| 20 | DeKalb County | 104238 |
| 21 | Vermilion County | 79209 |
| 22 | Williamson County | 67457 |
| 23 | Adams County | 66850 |
| 24 | Jackson County | 59249 |
| 25 | Whiteside County | 56943 |
| 26 | Boone County | 53571 |
| 27 | Coles County | 52217 |
| 28 | Ogle County | 51572 |
| 29 | Knox County | 51377 |
| 30 | Grundy County | 50358 |
| 31 | Henry County | 49654 |
| 32 | Macoupin County | 45887 |
| 33 | Stephenson County | 45680 |
| 34 | Franklin County | 39398 |
| 35 | Woodford County | 38949 |
| 36 | Marion County | 38381 |
| 37 | Jefferson County | 38290 |
| 38 | Clinton County | 37657 |
| 39 | Livingston County | 36615 |
| 40 | Fulton County | 35709 |
| 41 | Morgan County | 34693 |
| 42 | Lee County | 34521 |
| 43 | Effingham County | 34200 |
| 44 | Monroe County | 33811 |
| 45 | Bureau County | 33494 |
| 46 | Christian County | 33480 |
| 47 | Randolph County | 32754 |
| 48 | McDonough County | 31461 |
| 49 | Logan County | 29286 |
| 50 | Montgomery County | 29196 |
| 51 | Iroquois County | 28529 |
| 52 | Saline County | 24495 |
| 53 | Jersey County | 22268 |
| 54 | Jo Daviess County | 22068 |
| 55 | Fayette County | 22048 |
| 56 | Shelby County | 21819 |
| 57 | Perry County | 21522 |
| 58 | Douglas County | 19827 |
| 59 | Crawford County | 19262 |
| 60 | Hancock County | 18217 |
| 61 | Edgar County | 17625 |
| 62 | Warren County | 17448 |
| 63 | Union County | 17285 |
| 64 | Bond County | 16688 |
| 65 | Wayne County | 16534 |
| 66 | Lawrence County | 16467 |
| 67 | Piatt County | 16356 |
| 68 | De Witt County | 16185 |
| 69 | Richland County | 15952 |
| 70 | Clark County | 15881 |
| 71 | Pike County | 15794 |
| 72 | Mercer County | 15748 |
| 73 | Moultrie County | 14747 |
| 74 | Carroll County | 14638 |
| 75 | Massac County | 14568 |
| 76 | Washington County | 14259 |
| 77 | White County | 14204 |
| 78 | Mason County | 13862 |
| 79 | Ford County | 13527 |
| 80 | Clay County | 13395 |
| 81 | Greene County | 13345 |
| 82 | Cass County | 12843 |
| 83 | Johnson County | 12768 |
| 84 | Menard County | 12364 |
| 85 | Marshall County | 11925 |
| 86 | Wabash County | 11627 |
| 87 | Cumberland County | 10869 |
| 88 | Jasper County | 9630 |
| 89 | Hamilton County | 8247 |
| 90 | Schuyler County | 7150 |
| 91 | Henderson County | 7001 |
| 92 | Alexander County | 6763 |
| 93 | Brown County | 6755 |
| 94 | Edwards County | 6514 |
| 95 | Putnam County | 5729 |
| 96 | Pulaski County | 5662 |
| 97 | Stark County | 5508 |
| 98 | Gallatin County | 5224 |
| 99 | Scott County | 5112 |
| 100 | Calhoun County | 4858 |
| 101 | Pope County | 4302 |
| 102 | Hardin County | 4065 |