Founded in 1821, Hamilton County is one of 102 counties in the state of Illinois. Historically, Hamilton County was formed from White County. The city of McLeansboro is the county seat. With FIPS code of 65, Hamilton County has a population of 7,911 and area of 434 square miles (1,124 km2).
List of all cities in Hamilton County, IL alphabetically
| City/Town | Postal Code | Area Code |
| Belle Prairie City, IL | 62828 | 618/730 |
| Broughton, IL | 62817 | 618/730 |
| Crook, IL | 62859 | 618/730 |
| Dahlgren, IL | 62828 | 618/730 |
| Dale, IL | 62829 | 618/730 |
| Delafield, IL | 62859 | 618/730 |
| Knight Prairie, IL | 62859 | 618/730 |
| Macedonia, IL | 62860 | 618/730 |
| Mayberry, IL | 62817 | 618/730 |
| McLeansboro, IL | 62859 | 618/730 |
| Piopolis, IL | 62859 | 618/730 |
| South Crouch, IL | 62859 | 618/730 |
| South Twigg, IL | 62817 | 618/730 |
| Thackeray, IL | 62859 | 618/730 |
| Twigg, IL | 62829 | 618/730 |
| Walpole, IL | 62817 | 618/730 |