Founded in 1841, Mason County is one of 102 counties in the state of Illinois. Historically, Mason County was formed from Tazewell and Menard County. The city of Havana is the county seat. With FIPS code of 125, Mason County has a population of 12,881 and area of 539 square miles (1,396 km2).
List of all cities in Mason County, IL alphabetically
| City/Town | Postal Code | Area Code |
| Bath, IL | 62617 | 309 |
| Biggs, IL | 62633 | 309 |
| Bishop, IL | 61532 | 309 |
| Easton, IL | 62633 | 309 |
| Eckard, IL | 62644 | 309 |
| Enion, IL | 62644 | 309 |
| Forest City, IL | 61532 | 309 |
| Goofy Ridge, IL | 61567 | 309 |
| Havana, IL | 62644 | 309 |
| Kilbourne, IL | 62655 | 309 |
| Luther, IL | 62664 | 217 |
| Lynchburg, IL | 62617 | 309 |
| Manito, IL | 61546 | 309 |
| Mason City, IL | 62664 | 217 |
| Parkland, IL | 61546 | 309 |
| Poplar City, IL | 62633 | 309 |
| San Jose, IL | 62682 | 309 |
| Snicarte, IL | 62617 | 309 |
| Spring Lake, IL | 61546 | 309 |
| Talbott, IL | 61546 | 309 |
| Teheran, IL | 62664 | 217 |
| Topeka, IL | 61567 | 309 |