102 Counties — illinois
| County | Type | Population | Land area |
|---|
| adams | County | 68,277 | 857 sq mi |
| alexander | County | 9,590 | 236 sq mi |
| bond | County | 17,633 | 380 sq mi |
| boone | County | 41,786 | 281 sq mi |
| brown | County | 6,950 | 306 sq mi |
| bureau | County | 35,503 | 869 sq mi |
| calhoun | County | 5,084 | 254 sq mi |
| carroll | County | 16,674 | 444 sq mi |
| cass | County | 13,695 | 376 sq mi |
| champaign | County | 179,669 | 997 sq mi |
| christian | County | 35,372 | 709 sq mi |
| clark | County | 17,008 | 502 sq mi |
| clay | County | 14,560 | 469 sq mi |
| clinton | County | 35,535 | 474 sq mi |
| coles | County | 53,196 | 508 sq mi |
| cook | County | 5,376,741 | 946 sq mi |
| crawford | County | 20,452 | 444 sq mi |
| cumberland | County | 11,253 | 346 sq mi |
| dekalb | County | 88,969 | 634 sq mi |
| de witt | County | 16,798 | 398 sq mi |
| douglas | County | 19,922 | 417 sq mi |
| dupage | County | 904,161 | 334 sq mi |
| edgar | County | 19,704 | 624 sq mi |
| edwards | County | 6,971 | 222 sq mi |
| effingham | County | 34,264 | 479 sq mi |
| fayette | County | 21,802 | 717 sq mi |
| ford | County | 14,241 | 486 sq mi |
| franklin | County | 39,018 | 412 sq mi |
| fulton | County | 38,250 | 866 sq mi |
| gallatin | County | 6,445 | 324 sq mi |
| greene | County | 14,761 | 543 sq mi |
| grundy | County | 37,535 | 420 sq mi |
| hamilton | County | 8,621 | 435 sq mi |
| hancock | County | 20,121 | 795 sq mi |
| hardin | County | 4,800 | 178 sq mi |
| henderson | County | 8,213 | 379 sq mi |
| henry | County | 51,020 | 823 sq mi |
| iroquois | County | 31,334 | 1,117 sq mi |
| jackson | County | 59,612 | 588 sq mi |
| jasper | County | 10,117 | 494 sq mi |
| jefferson | County | 40,045 | 571 sq mi |
| jersey | County | 21,668 | 369 sq mi |
| jo daviess | County | 22,289 | 601 sq mi |
| johnson | County | 12,878 | 346 sq mi |
| kane | County | 404,119 | 521 sq mi |
| kankakee | County | 103,833 | 678 sq mi |
| kendall | County | 54,544 | 321 sq mi |
| knox | County | 55,836 | 716 sq mi |
| lake | County | 644,356 | 448 sq mi |
| lasalle | County | 111,509 | 1,135 sq mi |
| lawrence | County | 15,452 | 372 sq mi |
| lee | County | 36,062 | 725 sq mi |
| livingston | County | 39,678 | 1,044 sq mi |
| logan | County | 31,183 | 618 sq mi |
| macon | County | 114,706 | 581 sq mi |
| macoupin | County | 49,019 | 864 sq mi |
| madison | County | 258,941 | 725 sq mi |
| marion | County | 41,691 | 572 sq mi |
| marshall | County | 13,180 | 386 sq mi |
| mason | County | 16,038 | 539 sq mi |
| massac | County | 15,161 | 239 sq mi |
| mcdonough | County | 32,913 | 589 sq mi |
| mchenry | County | 260,077 | 604 sq mi |
| mclean | County | 150,433 | 1,184 sq mi |
| menard | County | 12,486 | 314 sq mi |
| mercer | County | 16,957 | 561 sq mi |
| monroe | County | 27,619 | 388 sq mi |
| montgomery | County | 30,652 | 704 sq mi |
| morgan | County | 36,616 | 569 sq mi |
| moultrie | County | 14,287 | 336 sq mi |
| ogle | County | 51,032 | 759 sq mi |
| peoria | County | 183,433 | 620 sq mi |
| perry | County | 23,094 | 441 sq mi |
| piatt | County | 16,365 | 440 sq mi |
| pike | County | 17,384 | 830 sq mi |
| pope | County | 4,413 | 371 sq mi |
| pulaski | County | 7,348 | 201 sq mi |
| putnam | County | 6,086 | 160 sq mi |
| randolph | County | 33,893 | 578 sq mi |
| richland | County | 16,149 | 360 sq mi |
| rock island | County | 149,374 | 427 sq mi |
| saline | County | 26,733 | 383 sq mi |
| sangamon | County | 188,951 | 868 sq mi |
| schuyler | County | 7,189 | 437 sq mi |
| scott | County | 5,537 | 251 sq mi |
| shelby | County | 22,893 | 759 sq mi |
| stark | County | 6,332 | 288 sq mi |
| st. clair | County | 256,082 | 664 sq mi |
| stephenson | County | 48,979 | 564 sq mi |
| tazewell | County | 128,485 | 649 sq mi |
| union | County | 18,293 | 416 sq mi |
| vermilion | County | 83,919 | 899 sq mi |
| wabash | County | 12,937 | 224 sq mi |
| warren | County | 18,735 | 543 sq mi |
| washington | County | 15,148 | 563 sq mi |
| wayne | County | 17,151 | 714 sq mi |
| white | County | 15,371 | 495 sq mi |
| whiteside | County | 60,653 | 685 sq mi |
| will | County | 502,266 | 837 sq mi |
| williamson | County | 61,296 | 424 sq mi |
| winnebago | County | 278,418 | 514 sq mi |
| woodford | County | 35,469 | 528 sq mi |