| City | Rank | 2026 Pop. ↓ | 2020 Pop. | Annual Change | Density (/mi²) | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Decatur | 1 | 67,179 | 71,225 | -1.04% | 1,521 | 44 | City |
| Mount Zion | 2 | 5,842 | 6,006 | -0.65% | 1,369 | 4 | Village |
| Forsyth | 3 | 3,587 | 3,733 | -0.72% | 1,159 | 3 | Village |
| Maroa | 4 | 1,504 | 1,580 | -0.86% | 853 | 2 | City |
| Harristown | 5 | 1,234 | 1,306 | -1.04% | 687 | 2 | Village |
| Long Creek | 6 | 1,202 | 1,255 | -0.83% | 426 | 3 | Village |
| Macon | 7 | 1,109 | 1,169 | -0.98% | 875 | 1 | City |
| Blue Mound | 8 | 1,067 | 1,129 | -1.02% | 1,824 | 1 | Village |
| Warrensburg | 9 | 1,059 | 1,111 | -0.84% | 1,455 | 1 | Village |
| Argenta | 10 | 863 | 913 | -1.03% | 1,322 | 1 | Village |
| Oreana | 11 | 836 | 885 | -1.07% | 1,786 | 0 | Village |
| Niantic | 12 | 571 | 609 | -1.21% | 550 | 1 | Village |
Decatur is the largest city in Macon County, with a population of 67,179.
Niantic is the smallest city in Macon County, with a population of 571.
There are 12 cities in Macon County, Illinois.