| City | Rank | 2026 Pop. ↓ | 2020 Pop. | Annual Change | Density (/mi²) | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Marshall | 1 | 3,862 | 3,950 | -0.46% | 1,053 | 4 | City |
| Casey | 2 | 2,360 | 2,429 | -0.59% | 900 | 3 | City |
| Martinsville | 3 | 1,076 | 1,113 | -0.65% | 532 | 2 | City |
| Westfield | 4 | 515 | 533 | -0.58% | 527 | 1 | Village |
Marshall is the largest city in Clark County, with a population of 3,862.
Westfield is the smallest city in Clark County, with a population of 515.
There are 4 cities in Clark County, Illinois.