23 cities
| City | Rank | 2026 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Springfield | 1 | 112,236 | 114,375 | -0.32% | 1,832 | 61 | City |
| Chatham | 2 | 14,751 | 14,415 | 0.38% | 1,992 | 7 | Village |
| Sherman | 3 | 4,615 | 4,671 | -0.19% | 1,469 | 3 | Village |
| Auburn | 4 | 4,406 | 4,546 | -0.52% | 1,068 | 4 | City |
| Rochester | 5 | 4,134 | 3,864 | 1.1% | 1,541 | 3 | Village |
| Riverton | 6 | 3,460 | 3,547 | -0.4% | 1,098 | 3 | Village |
| Pawnee | 7 | 2,705 | 2,683 | 0.15% | 2,031 | 1 | Village |
| Jerome | 8 | 1,626 | 1,686 | -0.61% | 3,519 | 0 | Village |
| Southern View | 9 | 1,532 | 1,589 | -0.58% | 2,287 | 1 | Village |
| Williamsville | 10 | 1,441 | 1,440 | 0% | 931 | 2 | Village |
| Leland Grove | 11 | 1,390 | 1,446 | -0.64% | 2,213 | 1 | City |
| Grandview | 12 | 1,375 | 1,411 | -0.43% | 4,104 | 0 | Village |
| New Berlin | 13 | 1,349 | 1,378 | -0.37% | 1,194 | 1 | Village |
| Divernon | 14 | 1,104 | 1,140 | -0.54% | 1,447 | 1 | Village |
| Illiopolis | 15 | 829 | 844 | -0.24% | 1,225 | 1 | Village |
| Pleasant Plains | 16 | 815 | 809 | 0.12% | 610 | 1 | Village |
| Loami | 17 | 791 | 809 | -0.38% | 782 | 1 | Village |
| Spaulding | 18 | 786 | 797 | -0.25% | 1,048 | 1 | Village |
| Mechanicsburg | 19 | 662 | 661 | 0% | 639 | 1 | Village |
| Thayer | 20 | 608 | 631 | -0.65% | 997 | 1 | Village |
| Dawson | 21 | 508 | 517 | -0.2% | 641 | 1 | Village |
| Buffalo | 22 | 431 | 446 | -0.46% | 1,249 | 0 | Village |
| Cantrall | 23 | 137 | 142 | -0.72% | 548 | 0 | Village |
Springfield is the largest city in Sangamon County, with a population of 112,236.
Cantrall is the smallest city in Sangamon County, with a population of 137.
There are 23 cities in Sangamon County, Illinois.