8 cities
| City | Rank | 2026 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Vienna | 1 | 1,349 | 1,352 | 0% | 476 | 3 | City |
| Goreville | 2 | 1,049 | 1,063 | -0.19% | 391 | 3 | Village |
| Vienna | 3 | 674 | 659 | 0.3% | 19 | 36 | Township |
| Cypress | 4 | 219 | 219 | 0% | 291 | 1 | Village |
| Buncombe | 5 | 207 | 207 | 0% | 174 | 1 | Village |
| New Burnside | 6 | 152 | 152 | 0% | 145 | 1 | Village |
| Belknap | 7 | 86 | 86 | 0% | 81 | 1 | Village |
| Simpson | 8 | 44 | 44 | 0% | 84 | 1 | Village |
Vienna is the largest city in Johnson County, with a population of 1,349.
Simpson is the smallest city in Johnson County, with a population of 44.
There are 8 cities in Johnson County, Illinois.