14 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Olney | 1 | 9,594 | 9,986 | -0.95% | 204 | 47 | Township |
| Olney | 2 | 8,366 | 8,691 | -0.77% | 1,207 | 7 | City |
| Noble | 3 | 1,381 | 1,432 | -0.86% | 33 | 41 | Township |
| Preston | 4 | 1,163 | 1,199 | -0.85% | 29 | 41 | Township |
| Claremont | 5 | 816 | 841 | -0.97% | 18 | 44 | Township |
| Noble | 6 | 608 | 630 | -0.82% | 598 | 1 | Village |
| Bonpas | 7 | 401 | 415 | -0.74% | 11 | 38 | Township |
| Decker | 8 | 401 | 415 | -0.99% | 11 | 35 | Township |
| Denver | 9 | 389 | 406 | -0.77% | 11 | 35 | Township |
| Dundas | 10 | 384 | 259 | 7.26% | 574 | 1 | CDP |
| German | 11 | 314 | 327 | -0.95% | 8 | 38 | Township |
| Parkersburg | 12 | 185 | 187 | -0.54% | 224 | 1 | Village |
| Claremont | 13 | 155 | 162 | -1.27% | 195 | 1 | Village |
| Calhoun | 14 | 152 | 159 | -1.3% | 167 | 1 | Village |
Olney is the largest city in Richland County, with a population of 9,594.
Calhoun is the smallest city in Richland County, with a population of 152.
There are 14 cities in Richland County, Illinois.