| City | Rank | 2026 Pop. ↓ | 2020 Pop. | Annual Change | Density (/mi²) | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Shelbyville | 1 | 4,511 | 4,640 | -0.57% | 1,104 | 4 | City |
| Lakewood | 2 | 4,296 | 4,272 | 0.07% | 937 | 5 | Village |
| Windsor | 3 | 1,027 | 1,067 | -0.77% | 1,630 | 1 | City |
| Stewardson | 4 | 715 | 719 | -0.14% | 1,166 | 1 | Village |
| Findlay | 5 | 653 | 670 | -0.76% | 707 | 1 | Village |
| Windsor | 6 | 644 | 670 | -0.77% | 1,470 | 0 | Village |
| Strasburg | 7 | 513 | 533 | -0.97% | 948 | 1 | Village |
| Cowden | 8 | 493 | 514 | -0.8% | 1,226 | 0 | Village |
| Tower Hill | 9 | 470 | 481 | -0.63% | 468 | 1 | Village |
| Herrick | 10 | 353 | 358 | -0.28% | 964 | 0 | Village |
| Sigel | 11 | 317 | 323 | -0.63% | 1,128 | 0 | Town |
| Oconee | 12 | 132 | 136 | -0.75% | 371 | 0 | Village |
Shelbyville is the largest city in Shelby County, with a population of 4,511.
Oconee is the smallest city in Shelby County, with a population of 132.
There are 12 cities in Shelby County, Illinois.