Founded in 1777, Washington County is one of 95 counties in the state of Tennessee. Historically, Washington County was formed from part of North Carolina. The city of Jonesborough is the county seat. With FIPS code of 179, Washington County has a population of 134,236 and area of 326 square miles (844 km2).
List of all cities in Washington County, TN alphabetically
| City/Town | Postal Code | Area Code |
| East TN State University, TN | 37614 | 423 |
| Fall Branch, TN | 37656 | 423 |
| Gray, TN | 37615 | 423 |
| Johnson City, TN | 37601 | 423 |
| 37602 | 423 | |
| 37604 | 423 | |
| 37605 | 423 | |
| 37614 | 423 | |
| 37615 | 423 | |
| Jonesborough, TN | 37659 | 423 |
| Limestone, TN | 37681 | 423 |
| Mountain Home, TN | 37684 | 423 |
| Telford, TN | 37690 | 423 |