5 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Marshall | 1 | 3,831 | 3,951 | -0.62% | 1,044 | 3.67 | City |
| Casey | 2 | 2,313 | 2,405 | -0.77% | 882 | 2.62 | City |
| Martinsville | 3 | 1,068 | 1,113 | -0.84% | 528 | 2.02 | City |
| Westfield | 4 | 513 | 535 | -0.77% | 525 | 0.98 | Village |
| West Union | 5 | 174 | 241 | -4.4% | 96 | 1.81 | CDP |
Marshall is the largest city in Clark County, with a population of 3,831.
West Union is the smallest city in Clark County.
There are 5 cities in Clark County, Illinois.