Founded in 1816, Monroe County is one of 102 counties in the state of Illinois. Historically, Monroe County was formed from Randolph County and St. Clair County. The city of Waterloo is the county seat. With FIPS code of 133, Monroe County has a population of 34,932 and area of 385 square miles (997 km2).
List of all cities in Monroe County, IL alphabetically
| City/Town | Postal Code | Area Code |
| Burksville, IL | 62298 | 618/730 |
| Chaflin Bridge, IL | 62244 | 618/730 |
| Columbia, IL | 62236 | 618/730 |
| Floraville, IL | 62298 | 618/730 |
| Foster Pond, IL | 62298 | 618/730 |
| Fountain, IL | 62295 | 618/730 |
| Fults, IL | 62244 | 618/730 |
| Harrisonville, IL | 62295 | 618/730 |
| Hecker, IL | 62248 | 618/730 |
| Lou del, IL | 62298 | 618/730 |
| Madonnaville, IL | 62298 | 618/730 |
| Maeystown, IL | 62256 | 618/730 |
| Merrimac, IL | 62295 | 618/730 |
| Monroe City, IL | 62298 | 618/730 |
| New Hanover, IL | 62298 | 618/730 |
| Paderborn, IL | 62298 | 618/730 |
| Renault, IL | 62279 | 618/730 |
| Saint Joe, IL | 62298 | 618/730 |
| Tipton, IL | 62298 | 618/730 |
| Valmeyer, IL | 62295 | 618/730 |
| Wartburg, IL | 62298 | 618/730 |
| Waterloo, IL | 62298 | 618/730 |