13 cities
| City | Rank | 2026 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Olney | 1 | 9,502 | 9,986 | -0.96% | 202 | 47 | Township |
| Olney | 2 | 8,301 | 8,691 | -0.78% | 1,198 | 7 | City |
| Noble | 3 | 1,369 | 1,432 | -0.87% | 33 | 41 | Township |
| Preston | 4 | 1,153 | 1,199 | -0.86% | 28 | 41 | Township |
| Claremont | 5 | 808 | 841 | -0.98% | 18 | 44 | Township |
| Noble | 6 | 604 | 630 | -0.66% | 594 | 1 | Village |
| Bonpas | 7 | 398 | 415 | -0.75% | 11 | 38 | Township |
| Decker | 8 | 397 | 415 | -1% | 11 | 35 | Township |
| Denver | 9 | 386 | 406 | -0.77% | 11 | 35 | Township |
| German | 10 | 311 | 327 | -0.96% | 8 | 38 | Township |
| Parkersburg | 11 | 185 | 187 | 0% | 224 | 1 | Village |
| Claremont | 12 | 154 | 162 | -0.65% | 194 | 1 | Village |
| Calhoun | 13 | 151 | 159 | -0.66% | 166 | 1 | Village |
Olney is the largest city in Richland County, with a population of 9,502.
Calhoun is the smallest city in Richland County, with a population of 151.
There are 13 cities in Richland County, Illinois.