| population | |
| Adams County | 65737 |
| Alexander County | 8238 |
| Bond County | 16725 |
| Boone County | 53544 |
| Brown County | 6578 |
| Bureau County | 34978 |
| Calhoun County | 5089 |
| Carroll County | 14305 |
| Cass County | 13642 |
| Champaign County | 201081 |
| Christian County | 34800 |
| Clark County | 15441 |
| Clay County | 13184 |
| Clinton County | 37762 |
| Coles County | 46863 |
| Cook County | 5194675 |
| Crawford County | 18807 |
| Cumberland County | 11048 |
| De Witt County | 16561 |
| DeKalb County | 105160 |
| Douglas County | 19740 |
| DuPage County | 916924 |
| Edgar County | 16866 |
| Edwards County | 6721 |
| Effingham County | 34242 |
| Fayette County | 22140 |
| Ford County | 13264 |
| Franklin County | 39561 |
| Fulton County | 37069 |
| Gallatin County | 5058 |
| Greene County | 13044 |
| Grundy County | 50063 |
| Hamilton County | 8457 |
| Hancock County | 19104 |
| population | |
| Hardin County | 3649 |
| Henderson County | 7331 |
| Henry County | 50486 |
| Iroquois County | 27604 |
| Jackson County | 60218 |
| Jasper County | 9698 |
| Jefferson County | 38827 |
| Jersey County | 21512 |
| Jo Daviess County | 22678 |
| Johnson County | 12582 |
| Kane County | 532403 |
| Kankakee County | 113449 |
| Kendall County | 114736 |
| Knox County | 52919 |
| Lake County | 714342 |
| LaSalle County | 113924 |
| Lawrence County | 16833 |
| Lee County | 36031 |
| Livingston County | 38950 |
| Logan County | 30305 |
| Macon County | 110768 |
| Macoupin County | 45313 |
| Madison County | 269282 |
| Marion County | 39437 |
| Marshall County | 12640 |
| Mason County | 13565 |
| Massac County | 15429 |
| McDonough County | 27238 |
| McHenry County | 308760 |
| McLean County | 169572 |
| Menard County | 12705 |
| Mercer County | 16434 |
| Monroe County | 32957 |
| Montgomery County | 30104 |
| population | |
| Morgan County | 35547 |
| Moultrie County | 14526 |
| Ogle County | 53497 |
| Peoria County | 179179 |
| Perry County | 21174 |
| Piatt County | 16673 |
| Pike County | 15611 |
| Pope County | 4212 |
| Pulaski County | 6161 |
| Putnam County | 6006 |
| Randolph County | 33476 |
| Richland County | 15763 |
| Rock Island County | 147546 |
| Saint Clair County | 257400 |
| Saline County | 23768 |
| Sangamon County | 194672 |
| Schuyler County | 6907 |
| Scott County | 5355 |
| Shelby County | 20990 |
| Stark County | 5427 |
| Stephenson County | 44753 |
| Tazewell County | 131803 |
| Union County | 17808 |
| Vermilion County | 81625 |
| Wabash County | 11947 |
| Warren County | 17707 |
| Washington County | 14716 |
| Wayne County | 16760 |
| White County | 13665 |
| Whiteside County | 55626 |
| Will County | 677560 |
| Williamson County | 66357 |
| Winnebago County | 295266 |
| Woodford County | 38463 |
 | Decatur Airport | ~ 37.63 km |
| Abraham Lincoln Capital Airport | ~ 40.39 km |
| Central Illinois Regional Airport at Bloomington-Normal | ~ 60.14 km |
| General Wayne A. Downing Peoria International Airport | ~ 82.82 km |
| University of Illinois Willard Airport | ~ 83.07 km |
| Coles County Memorial Airport | ~ 101.34 km |
| Vandalia Municipal Airport | ~ 112.41 km |
| Greenville Airport | ~ 129.83 km |
| Macomb Municipal Airport | ~ 132.26 km |
