Illinois Counties by Population (2025)
2025 Pop.
500K
1M
1.5M
2M
2.5M
3M
3.5M
4M
4.5M
5M
Top 5 Most Populous Counties
5,222,712
945,104
723,001
713,783
524,753
102 Counties
| County | 2025 Pop. ↓ | Area (mi²) | Density | Change (2020) |
|---|---|---|---|---|
| Cook County | 5,222,712 | 945 | 5,527 | -0.84% |
| DuPage County | 945,104 | 328 | 2,881 | 1.46% |
| Lake County | 723,001 | 444 | 1,628 | 1.34% |
| Will County | 713,783 | 836 | 854 | 2.42% |
| Kane County | 524,753 | 519 | 1,011 | 1.62% |
| McHenry County | 318,483 | 603 | 528 | 2.75% |
| Winnebago County | 285,366 | 513 | 556 | 0.14% |
| Madison County | 262,592 | 716 | 367 | -1.19% |
| St. Clair County | 250,204 | 658 | 380 | -2.67% |
| Champaign County | 214,935 | 1K | 216 | 4.21% |
| Sangamon County | 194,474 | 868 | 224 | -0.89% |
| Peoria County | 180,525 | 619 | 292 | -0.54% |
| McLean County | 172,645 | 1.2K | 146 | 0.82% |
| Kendall County | 146,113 | 320 | 457 | 10.4% |
| Rock Island County | 143,523 | 427 | 336 | -0.58% |
| Tazewell County | 129,807 | 646 | 201 | -1.13% |
| LaSalle County | 108,383 | 1.1K | 95 | -0.94% |
| Kankakee County | 106,434 | 676 | 157 | -0.9% |
| DeKalb County | 102,009 | 631 | 162 | 1.63% |
| Macon County | 100,720 | 581 | 173 | -2.93% |
| Vermilion County | 70,661 | 898 | 79 | -4.53% |
| Williamson County | 67,391 | 420 | 160 | 0.4% |
| Adams County | 63,783 | 855 | 75 | -2.8% |
| Whiteside County | 54,732 | 684 | 80 | -1.52% |
| Grundy County | 54,083 | 418 | 129 | 2.95% |
| Jackson County | 53,531 | 584 | 92 | 0.5% |
| Boone County | 53,387 | 281 | 190 | 0.09% |
| Ogle County | 51,299 | 759 | 68 | -0.89% |
| Knox County | 48,769 | 716 | 68 | -2.08% |
| Henry County | 47,992 | 823 | 58 | -2.41% |
| Coles County | 46,314 | 508 | 91 | -1.64% |
| Macoupin County | 43,663 | 863 | 51 | -2.81% |
| Stephenson County | 42,829 | 564 | 76 | -3.91% |
| Woodford County | 38,193 | 528 | 72 | -0.56% |
| Clinton County | 37,288 | 474 | 79 | 1.02% |
| Franklin County | 36,910 | 409 | 90 | -2.14% |
| Marion County | 36,234 | 573 | 63 | -3.78% |
| Jefferson County | 35,883 | 571 | 63 | -3.02% |
| Livingston County | 35,429 | 1K | 34 | -1.08% |
| Monroe County | 34,794 | 385 | 90 | -0.45% |
| Effingham County | 34,751 | 479 | 73 | 0.13% |
| Lee County | 33,482 | 725 | 46 | -1.71% |
| Christian County | 33,175 | 709 | 47 | -2.37% |
| Morgan County | 32,463 | 569 | 57 | -3.08% |
| Fulton County | 32,356 | 866 | 37 | -3.57% |
| Bureau County | 32,214 | 869 | 37 | -3.04% |
| Randolph County | 29,813 | 575 | 52 | -0.9% |
| Logan County | 27,528 | 618 | 45 | -1.35% |
| Montgomery County | 27,474 | 704 | 39 | -2.72% |
| McDonough County | 26,372 | 589 | 45 | -2.74% |
| Iroquois County | 26,101 | 1.1K | 23 | -3.21% |
| Saline County | 22,664 | 380 | 60 | -4.54% |
| Jo Daviess County | 21,307 | 601 | 35 | -3.58% |
| Jersey County | 21,142 | 370 | 57 | -1.63% |
| Fayette County | 21,105 | 716 | 29 | -1.77% |
| Shelby County | 20,491 | 759 | 27 | -1.99% |
| Perry County | 20,045 | 442 | 45 | -4.05% |
| Douglas County | 19,915 | 417 | 48 | 0.68% |
| Crawford County | 18,434 | 444 | 42 | -1.09% |
| Union County | 16,906 | 413 | 41 | -2.27% |
| Hancock County | 16,821 | 794 | 21 | -4.2% |
| Piatt County | 16,536 | 439 | 38 | -0.88% |
| Bond County | 16,515 | 380 | 43 | -2.02% |
| Edgar County | 16,354 | 623 | 26 | -2.7% |
| Warren County | 16,210 | 542 | 30 | -3.7% |
| Wayne County | 15,981 | 714 | 22 | -1.11% |
| Carroll County | 15,396 | 445 | 35 | -1.8% |
| De Witt County | 15,307 | 398 | 38 | -1.02% |
| Richland County | 15,222 | 360 | 42 | -3.69% |
| Mercer County | 15,128 | 561 | 27 | -3.22% |
| Clark County | 14,934 | 501 | 30 | -3.33% |
| Lawrence County | 14,716 | 372 | 40 | -3.71% |
| Moultrie County | 14,403 | 336 | 43 | -0.61% |
| Pike County | 14,177 | 831 | 17 | -3.14% |
| Ford County | 13,586 | 486 | 28 | 0.56% |
| Massac County | 13,503 | 237 | 57 | -4.48% |
| Washington County | 13,500 | 563 | 24 | -1.68% |
| White County | 13,308 | 495 | 27 | -3.66% |
| Johnson County | 13,285 | 344 | 39 | -0.28% |
| Clay County | 12,697 | 468 | 27 | -4.34% |
| Cass County | 12,647 | 376 | 34 | -2.54% |
| Mason County | 12,498 | 539 | 23 | -4.25% |
| Menard County | 11,930 | 314 | 38 | -2.79% |
| Marshall County | 11,454 | 387 | 30 | -2.19% |
| Greene County | 11,262 | 543 | 21 | -5.64% |
| Wabash County | 10,926 | 223 | 49 | -3.44% |
| Cumberland County | 10,338 | 346 | 30 | -0.95% |
| Jasper County | 9,028 | 495 | 18 | -2.45% |
| Hamilton County | 7,750 | 435 | 18 | -3.04% |
| Schuyler County | 6,775 | 437 | 16 | -1.38% |
| Brown County | 6,313 | 306 | 21 | 1.22% |
| Henderson County | 5,991 | 379 | 16 | -5.43% |
| Edwards County | 5,947 | 222 | 27 | -4.22% |
| Putnam County | 5,678 | 160 | 35 | 0.83% |
| Stark County | 5,277 | 288 | 18 | -2.06% |
| Scott County | 4,910 | 251 | 20 | -3.23% |
| Pulaski County | 4,801 | 199 | 24 | -7.3% |
| Gallatin County | 4,672 | 323 | 14 | -5.52% |
| Alexander County | 4,465 | 235 | 19 | -13.67% |
| Calhoun County | 4,155 | 254 | 16 | -5.63% |
| Pope County | 3,691 | 369 | 10 | -1.78% |
| Hardin County | 3,501 | 177 | 20 | -3.98% |
Overview of Illinois Counties
There are 102 counties in Illinois.
Cook County is the largest county in the state, with a population of 5,222,712. The most recent census shows that its population has decreased by 0.01% since the previous census.
A number of other Illinois counties also boast relatively large populations for their state, though not able to match the density of Cook County:
- DuPage County : 945,104
- Lake County : 723,001
Illinois Counties with the Fewest Residents
The smallest county in Illinois is Hardin County , with a population of just 3,501. This total represents a decrease of 0.0% since the last census count was performed.
Other small counties include:
- Pope County : 3,691
- Calhoun County : 4,155
- Alexander County : 4,465
Illinois Counties with Rapid Growth
Kendall County , with its sizeable population of 146,113, has shown the largest population growth, with an increase of 0.1% since the last census.
Will County has also had relatively high population growth of 0.02% with 713,783 residents.
On the other hand, Alexander County has had the largest decrease in population, with its 4,465 current residents totalling 0.1% less than the previous census.
Sources
- US Census State Population Estimates - Most recent state estimates from the Census Bureau's Population Estimates Program
- US Census County Population Estimates - Most recent county estimates from the Census Bureau's Population Estimates Program
- American Community Survey (2009 - 2013)
- Census QuickFacts
- Historical Populations of States and Counties (1790 - 1990)