4 cities
| City | Rank | 2026 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Marshall | 1 | 3,822 | 3,951 | -0.55% | 1,042 | 4 | City |
| Casey | 2 | 2,348 | 2,432 | -0.59% | 895 | 3 | City |
| Martinsville | 3 | 1,068 | 1,113 | -0.65% | 528 | 2 | City |
| Westfield | 4 | 512 | 535 | -0.78% | 524 | 1 | Village |
Marshall is the largest city in Clark County, with a population of 3,822.
Westfield is the smallest city in Clark County, with a population of 512.
There are 4 cities in Clark County, Illinois.