# Counties in Illinois by median age on 1 July (US county estimates), 2025

All 102 values come from U.S. Census Bureau for 2025, so the places are comparable.

- Indicator id: `median_age_pep`
- Unit: years
- Definition: Age that divides the resident population of a US county into two halves of equal size on 1 July, from Census Bureau population estimates calculated by single year of age.
- Source: U.S. Census Bureau, Population Estimates Program, county population by age and sex: median age (MEDIAN_AGE_TOT) on 1 July, 2010 to 2019 from the 2010 to 2020 intercensal file and 2020 onwards from the latest vintage (https://www.census.gov/programs-surveys/popest/data/data-sets.html)
- Publisher page: https://invokely.ai/en/publishers/us-census-bureau
- Retrieved: 2026-10-12
- Citation: U.S. Census Bureau. Population Estimates Program, county population by age and sex: median age (MEDIAN_AGE_TOT) on 1 July, 2010 to 2019 from the 2010 to 2020 intercensal file and 2020 onwards from the latest vintage. https://www.census.gov/programs-surveys/popest/data/data-sets.html. Retrieved 2026-10-12.
- Web page: https://invokely.ai/rankings/median-age-july-1-us-counties/illinois-counties

| Rank | Place | years |
|---:|---|---:|
| 1 | Pope County | 54.6 |
| 2 | Jo Daviess County | 51.3 |
| 3 | Henderson County | 51.2 |
| 4 | Hardin County | 50.6 |
| 5 | Alexander County | 49.9 |
| 6 | Schuyler County | 49.7 |
| 7 | Calhoun County | 49.2 |
| 8 | Gallatin County | 48.4 |
| 9 | Putnam County | 46.7 |
| 10 | Carroll County | 46.6 |
| 10 | Scott County | 46.6 |
| 12 | Hancock County | 46.2 |
| 12 | Mason County | 46.2 |
| 14 | Edgar County | 45.6 |
| 14 | Marshall County | 45.6 |
| 16 | Massac County | 45.5 |
| 16 | Shelby County | 45.5 |
| 18 | Edwards County | 45.4 |
| 19 | Stephenson County | 45.3 |
| 20 | Bureau County | 45.1 |
| 20 | Washington County | 45.1 |
| 22 | Macoupin County | 45 |
| 23 | Jersey County | 44.9 |
| 23 | Mercer County | 44.9 |
| 25 | Pulaski County | 44.8 |
| 25 | Union County | 44.8 |
| 27 | Iroquois County | 44.6 |
| 27 | Menard County | 44.6 |
| 27 | White County | 44.6 |
| 30 | Fulton County | 44.5 |
| 30 | Monroe County | 44.5 |
| 32 | Lee County | 44.4 |
| 33 | Greene County | 44.1 |
| 34 | Henry County | 44 |
| 34 | Jasper County | 44 |
| 34 | Saline County | 44 |
| 37 | Christian County | 43.9 |
| 37 | Franklin County | 43.9 |
| 39 | Clark County | 43.7 |
| 39 | De Witt County | 43.7 |
| 39 | Whiteside County | 43.7 |
| 42 | Montgomery County | 43.6 |
| 42 | Richland County | 43.6 |
| 42 | Stark County | 43.6 |
| 45 | Cumberland County | 43.5 |
| 46 | Piatt County | 43.4 |
| 46 | Randolph County | 43.4 |
| 46 | Wabash County | 43.4 |
| 49 | Hamilton County | 43.2 |
| 49 | Knox County | 43.2 |
| 49 | LaSalle County | 43.2 |
| 49 | Williamson County | 43.2 |
| 53 | Clay County | 43.1 |
| 54 | Johnson County | 43 |
| 54 | Marion County | 43 |
| 56 | Crawford County | 42.8 |
| 56 | Lawrence County | 42.8 |
| 58 | Jefferson County | 42.6 |
| 58 | Perry County | 42.6 |
| 58 | Wayne County | 42.6 |
| 61 | Tazewell County | 42.5 |
| 62 | Ogle County | 42.4 |
| 63 | Morgan County | 42.3 |
| 63 | Woodford County | 42.3 |
| 65 | Livingston County | 42.2 |
| 66 | Adams County | 42.1 |
| 66 | Ford County | 42.1 |
| 66 | Pike County | 42.1 |
| 69 | Clinton County | 42 |
| 69 | Sangamon County | 42 |
| 71 | Logan County | 41.9 |
| 71 | Moultrie County | 41.9 |
| 73 | Macon County | 41.8 |
| 74 | McHenry County | 41.6 |
| 74 | Vermilion County | 41.6 |
| 76 | Effingham County | 41.4 |
| 77 | Fayette County | 41.2 |
| 78 | Madison County | 41.1 |
| 79 | DuPage County | 41 |
| 79 | Warren County | 41 |
| 81 | Boone County | 40.7 |
| 82 | Brown County | 40.6 |
| 82 | Rock Island County | 40.6 |
| 84 | St. Clair County | 40.5 |
| 85 | Bond County | 40.4 |
| 86 | Kankakee County | 40.3 |
| 87 | Lake County | 40.2 |
| 88 | Will County | 40 |
| 88 | Winnebago County | 40 |
| 90 | Grundy County | 39.7 |
| 91 | Cass County | 39.6 |
| 92 | Kane County | 39.5 |
| 93 | Douglas County | 38.9 |
| 94 | Peoria County | 38.7 |
| 95 | Cook County | 38.4 |
| 96 | Coles County | 38.2 |
| 97 | Kendall County | 36.8 |
| 98 | McDonough County | 36.4 |
| 99 | McLean County | 35.5 |
| 100 | DeKalb County | 34.1 |
| 101 | Jackson County | 33 |
| 102 | Champaign County | 31 |