14 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Olney township | 1 | 9,674 | 9,973 | -0.47% | 205 | 47.14 | Township |
| Olney | 2 | 8,392 | 8,691 | -0.71% | 1,211 | 6.93 | City |
| Noble township | 3 | 1,394 | 1,431 | -0.43% | 34 | 41.26 | Township |
| Preston township | 4 | 1,166 | 1,197 | -0.43% | 29 | 40.73 | Township |
| Claremont township | 5 | 834 | 842 | -0.12% | 19 | 44.13 | Township |
| Noble | 6 | 613 | 630 | -0.49% | 603 | 1.02 | Village |
| Bonpas township | 7 | 409 | 418 | -0.24% | 11 | 37.50 | Township |
| Decker township | 8 | 403 | 414 | -0.49% | 11 | 35.24 | Township |
| Denver township | 9 | 392 | 407 | -0.51% | 11 | 35.40 | Township |
| Dundas | 10 | 384 | 259 | 7.26% | 574 | 0.67 | CDP |
| German township | 11 | 319 | 327 | -0.31% | 8 | 37.80 | Township |
| Parkersburg | 12 | 183 | 185 | 0% | 222 | 0.83 | Village |
| Claremont | 13 | 158 | 163 | -0.63% | 199 | 0.79 | Village |
| Calhoun | 14 | 156 | 161 | -0.64% | 171 | 0.91 | Village |
Olney township is the largest city in Richland County, with a population of 9,674.
Calhoun is the smallest city in Richland County.
There are 14 cities in Richland County, Illinois.