| City | Rank | 2026 Pop. ↓ | 2020 Pop. | Annual Change | Density (/mi²) | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Springfield | 1 | 112,630 | 114,431 | -0.32% | 1,839 | 61 | City |
| Chatham | 2 | 14,620 | 14,425 | 0.28% | 1,974 | 7 | Village |
| Sherman | 3 | 4,632 | 4,671 | -0.26% | 1,474 | 3 | Village |
| Auburn | 4 | 4,416 | 4,542 | -0.59% | 1,071 | 4 | City |
| Rochester | 5 | 4,134 | 3,863 | 1% | 1,541 | 3 | Village |
| Riverton | 6 | 3,452 | 3,549 | -0.55% | 1,096 | 3 | Village |
| Pawnee | 7 | 2,688 | 2,680 | 0.07% | 2,018 | 1 | Village |
| Jerome | 8 | 1,616 | 1,674 | -0.68% | 3,498 | 0 | Village |
| Southern View | 9 | 1,530 | 1,585 | -0.65% | 2,284 | 1 | Village |
| Williamsville | 10 | 1,436 | 1,439 | -0.07% | 928 | 2 | Village |
| Leland Grove | 11 | 1,391 | 1,443 | -0.71% | 2,215 | 1 | City |
| Grandview | 12 | 1,382 | 1,416 | -0.5% | 4,125 | 0 | Village |
| New Berlin | 13 | 1,355 | 1,379 | -0.44% | 1,199 | 1 | Village |
| Divernon | 14 | 1,100 | 1,138 | -0.63% | 1,442 | 1 | Village |
| Illiopolis | 15 | 829 | 845 | -0.36% | 1,225 | 1 | Village |
| Pleasant Plains | 16 | 822 | 823 | -0.12% | 616 | 1 | Village |
| Spaulding | 17 | 787 | 798 | -0.38% | 1,049 | 1 | Village |
| Loami | 18 | 785 | 810 | -0.63% | 776 | 1 | Village |
| Mechanicsburg | 19 | 660 | 658 | -0.15% | 637 | 1 | Village |
| Thayer | 20 | 610 | 633 | -0.81% | 1,000 | 1 | Village |
| Dawson | 21 | 504 | 516 | -0.59% | 636 | 1 | Village |
| Buffalo | 22 | 434 | 446 | -0.69% | 1,258 | 0 | Village |
| Cantrall | 23 | 137 | 141 | -0.72% | 548 | 0 | Village |
Springfield is the largest city in Sangamon County, with a population of 112,630.
Cantrall is the smallest city in Sangamon County, with a population of 137.
There are 23 cities in Sangamon County, Illinois.