Ranking of Illinois Counties By Population Aged 25 years and above with an Educational attainment of Less than High School Diploma in 2021 (ACS-5Yrs)
Updated on September 3, 2025.
Based on the US Census ACS-5Yrs estimates, in 2021, the population of Illinois (aged 25 years and above) who had an educational attainment of Less than High School Diploma was 885,321. Among all Illinois counties, Cook County had the highest population (aged 25 years and above) with an educational attainment of Less than High School Diploma (439,740), followed by Kane County (47,621), and Lake County (43,130).
The chart below shows the top 10 Illinois counties, and the table below shows the ranking of all Illinois counties.
You can see similar information for other educational attainments.
You can also see similar information for other states and for the United States.
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Related Topics: Illinois ACS-5Yrs Estimates, 2021 Topic List.
Data Source: US Census - ACS 5-Year Estimates.
Ranking of Illinois Counties By Population (Aged 25yrs+) with an Educational Attainment of Less than High School Diploma in 2021
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| Rank | County | Number of People |
|---|---|---|
| 1 | Cook County | 439740 |
| 2 | Kane County | 47621 |
| 3 | Lake County | 43130 |
| 4 | DuPage County | 41827 |
| 5 | Will County | 39246 |
| 6 | Winnebago County | 22994 |
| 7 | McHenry County | 13717 |
| 8 | St. Clair County | 13631 |
| 9 | Madison County | 13030 |
| 10 | Rock Island County | 10918 |
| 11 | Sangamon County | 9898 |
| 12 | Peoria County | 9588 |
| 13 | Kankakee County | 7490 |
| 14 | LaSalle County | 7334 |
| 15 | Champaign County | 6294 |
| 16 | Tazewell County | 6260 |
| 17 | Macon County | 5926 |
| 18 | Kendall County | 5307 |
| 19 | Vermilion County | 4997 |
| 20 | Boone County | 4575 |
| 21 | DeKalb County | 4404 |
| 22 | McLean County | 4190 |
| 23 | Knox County | 3859 |
| 24 | Williamson County | 3506 |
| 25 | Adams County | 3475 |
| 26 | Whiteside County | 3399 |
| 27 | Randolph County | 3309 |
| 28 | Ogle County | 3255 |
| 29 | Marion County | 2885 |
| 30 | Macoupin County | 2857 |
| 31 | Franklin County | 2809 |
| 32 | Jackson County | 2710 |
| 33 | Henry County | 2694 |
| 34 | Jefferson County | 2644 |
| 35 | Lee County | 2607 |
| 36 | Fulton County | 2595 |
| 37 | Stephenson County | 2576 |
| 38 | Christian County | 2569 |
| 39 | Montgomery County | 2514 |
| 40 | Perry County | 2500 |
| 41 | Livingston County | 2492 |
| 42 | Coles County | 2465 |
| 43 | Morgan County | 2451 |
| 44 | Clinton County | 2297 |
| 45 | Iroquois County | 2234 |
| 46 | Bureau County | 2230 |
| 46 | Grundy County | 2230 |
| 47 | Douglas County | 2118 |
| 48 | Saline County | 2087 |
| 49 | Fayette County | 2071 |
| 50 | Logan County | 1906 |
| 51 | Crawford County | 1886 |
| 52 | Lawrence County | 1765 |
| 53 | Johnson County | 1635 |
| 54 | Effingham County | 1631 |
| 55 | Edgar County | 1493 |
| 56 | Woodford County | 1484 |
| 57 | Wayne County | 1438 |
| 58 | Carroll County | 1376 |
| 59 | Bond County | 1345 |
| 60 | Union County | 1337 |
| 61 | Warren County | 1335 |
| 62 | Moultrie County | 1322 |
| 63 | Cass County | 1320 |
| 64 | Massac County | 1297 |
| 65 | Jo Daviess County | 1280 |
| 66 | Monroe County | 1155 |
| 67 | Jersey County | 1139 |
| 68 | Clay County | 1082 |
| 69 | Shelby County | 1035 |
| 70 | White County | 1030 |
| 71 | Pike County | 920 |
| 72 | Mason County | 895 |
| 73 | Brown County | 893 |
| 74 | Hancock County | 846 |
| 75 | Richland County | 843 |
| 76 | Mercer County | 842 |
| 77 | McDonough County | 821 |
| 78 | Greene County | 804 |
| 79 | Washington County | 785 |
| 80 | Ford County | 779 |
| 81 | De Witt County | 771 |
| 82 | Clark County | 756 |
| 83 | Piatt County | 740 |
| 84 | Hamilton County | 676 |
| 85 | Wabash County | 658 |
| 86 | Marshall County | 648 |
| 87 | Alexander County | 527 |
| 88 | Cumberland County | 525 |
| 89 | Jasper County | 520 |
| 90 | Hardin County | 445 |
| 91 | Gallatin County | 442 |
| 92 | Pulaski County | 404 |
| 92 | Schuyler County | 404 |
| 92 | Stark County | 404 |
| 93 | Menard County | 371 |
| 94 | Henderson County | 367 |
| 95 | Edwards County | 347 |
| 96 | Pope County | 316 |
| 97 | Putnam County | 275 |
| 98 | Calhoun County | 241 |
| 99 | Scott County | 210 |