Founded in 1729, Washington County is one of 5 counties in the state of Rhode Island. Historically, Washington County was formed in 1729 as Kings County from part of Providence Plantations County which was renamed Washington County in 1781. The city of South Kingstown is the county seat. With FIPS code of 9, Washington County has a population of 130,592 and area of 329 square miles (852 km2).
List of all cities in Washington County, RI alphabetically
| City/Town | Postal Code | Area Code |
| Ashaway, RI | 02804 | 401 |
| Block Island, RI | 02807 | 401 |
| Bonnet Shores, RI | 02882 | 401 |
| Bradford, RI | 02808 | 401 |
| Carolina, RI | 02812 | 401 |
| Charlestown, RI | 02813 | 401 |
| 02836 | 401 | |
| Davisville, RI | 02852 | 401 |
| East Matunuck, RI | 02879 | 401 |
| Escoheag, RI | 02822 | 401 |
| Exeter, RI | 02822 | 401 |
| Galilee, RI | 02882 | 401 |
| Green Hill, RI | 02879 | 401 |
| Hope Valley, RI | 02832 | 401 |
| Hopkinton, RI | 02804 | 401 |
| 02808 | 401 | |
| 02832 | 401 | |
| 02833 | 401 | |
| 02873 | 401 | |
| Jerusalem, RI | 02879 | 401 |
| Kenyon, RI | 02836 | 401 |
| Kingston, RI | 02881 | 401 |
| Matunuck, RI | 02879 | 401 |
| Misquamicut, RI | 02891 | 401 |
| Narragansett, RI | 02874 | 401 |
| 02879 | 401 | |
| 02882 | 401 | |
| New Shoreham, RI | 02807 | 401 |
| North Kingstown, RI | 02852 | 401 |
| 02854 | 401 | |
| 02874 | 401 | |
| Peace Dale, RI | 02879 | 401 |
| 02883 | 401 | |
| Point Judith, RI | 02882 | 401 |
| Richmond, RI | 02812 | 401 |
| 02832 | 401 | |
| 02836 | 401 | |
| 02875 | 401 | |
| 02892 | 401 | |
| 02898 | 401 | |
| Rockville, RI | 02873 | 401 |
| Saunderstown, RI | 02874 | 401 |
| Shannock, RI | 02875 | 401 |
| Slocum, RI | 02877 | 401 |
| South Kingstown, RI | 02879 | 401 |
| 02883 | 401 | |
| 02892 | 401 | |
| Wakefield, RI | 02879 | 401 |
| 02880 | 401 | |
| 02881 | 401 | |
| 02883 | 401 | |
| Watch Hill, RI | 02891 | 401 |
| West Kingston, RI | 02892 | 401 |
| Westerly, RI | 02808 | 401 |
| 02891 | 401 | |
| Wickford, RI | 02852 | 401 |
| Wood River Junction, RI | 02894 | 401 |
| Wyoming, RI | 02898 | 401 |