Founded in 1827, Sullivan County is one of 10 counties in the state of New Hampshire. Historically, Sullivan County was formed from part of Cheshire County. The city of Newport is the county seat. With FIPS code of 19, Sullivan County has a population of 43,063 and area of 537 square miles (1,391 km2).
List of all cities in Sullivan County, NH alphabetically
| City/Town | Postal Code | Area Code |
| Acworth, NH | 03601 | 603 |
| Charlestown, NH | 03603 | 603 |
| Claremont, NH | 03743 | 603 |
| Cornish, NH | 03745 | 603 |
| Cornish Flat, NH | 03746 | 603 |
| Croydon, NH | 03773 | 603 |
| East Lempster, NH | 03605 | 603 |
| Georges Mills, NH | 03751 | 603 |
| Goshen, NH | 03752 | 603 |
| Grantham, NH | 03753 | 603 |
| Guild, NH | 03754 | 603 |
| Lempster, NH | 03605 | 603 |
| Meriden, NH | 03770 | 603 |
| Newport, NH | 03773 | 603 |
| Plainfield, NH | 03781 | 603 |
| So Acworth, NH | 03607 | 603 |
| South Acworth, NH | 03607 | 603 |
| Springfield, NH | 03284 | 603 |
| Sunapee, NH | 03782 | 603 |
| Unity, NH | 03603 | 603 |
| 03743 | 603 | |
| 03773 | 603 | |
| Washington, NH | 03280 | 603 |
| West Springfield, NH | 03284 | 603 |