Founded in 1818, Washington County is one of 102 counties in the state of Illinois. Historically, Washington County was formed from St. Clair County. The city of Nashville is the county seat. With FIPS code of 189, Washington County has a population of 13,655 and area of 562 square miles (1,456 km2).
List of all cities in Washington County, IL alphabetically
| City/Town | Postal Code | Area Code |
| Addieville, IL | 62214 | 618/730 |
| Ashley, IL | 62808 | 618/730 |
| Beaucoup, IL | 62263 | 618/730 |
| Bolo, IL | 62808 | 618/730 |
| Covington, IL | 62271 | 618/730 |
| Du Bois, IL | 62831 | 618/730 |
| Dubois, IL | 62831 | 618/730 |
| Elkton, IL | 62268 | 618/730 |
| Hoyleton, IL | 62803 | 618/730 |
| Huegely, IL | 62803 | 618/730 |
| Irvington, IL | 62848 | 618/730 |
| Lively Grove, IL | 62268 | 618/730 |
| Nashville, IL | 62263 | 618/730 |
| New Minden, IL | 62263 | 618/730 |
| Oakdale, IL | 62268 | 618/730 |
| Okawville, IL | 62271 | 618/730 |
| Pilot Knob, IL | 62263 | 618/730 |
| Radom, IL | 62876 | 618/730 |
| Richview, IL | 62877 | 618/730 |
| Todds Mill, IL | 62263 | 618/730 |
| Venedy, IL | 62214 | 618/730 |