| City | Rank | 2026 Pop. ↓ | 2020 Pop. | Annual Change | Density (/mi²) | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Effingham | 1 | 12,427 | 12,330 | 0.17% | 1,141 | 11 | City |
| Altamont | 2 | 2,179 | 2,217 | -0.32% | 1,418 | 2 | City |
| Teutopolis | 3 | 1,737 | 1,627 | 0.93% | 850 | 2 | Village |
| Dieterich | 4 | 878 | 897 | -0.45% | 643 | 1 | Village |
| Watson | 5 | 655 | 669 | -0.46% | 600 | 1 | Village |
| Beecher City | 6 | 424 | 428 | -0.24% | 474 | 1 | Village |
| Edgewood | 7 | 388 | 397 | -0.51% | 383 | 1 | Village |
| Mason | 8 | 319 | 324 | -0.62% | 248 | 1 | Town |
| Montrose | 9 | 210 | 213 | -0.47% | 330 | 1 | Village |
| Shumway | 10 | 184 | 188 | -0.54% | 554 | 0 | Village |
Effingham is the largest city in Effingham County, with a population of 12,427.
Shumway is the smallest city in Effingham County, with a population of 184.
There are 10 cities in Effingham County, Illinois.