The largest county in New Hampshire
There are two right answers. By land area it is Coos County; by population it is Hillsborough County. Which one you want depends on what you meant by largest.
Sources: US Census Bureau, Population Estimates Program, Vintage 2025 Population Estimates, released 26 March 2026; US Census Bureau, Gazetteer Files, 2025 Gazetteer Files, released 10 September 2025. Retrieved 30 August 2026.
By land area
| Rank | Name | Land area | Population |
|---|---|---|---|
| 1 | Coos County | 1,795 sq mi | 31,343 |
| 2 | Grafton County | 1,709 sq mi | 93,225 |
| 3 | Merrimack County | 932.9 sq mi | 158,078 |
| 4 | Carroll County | 931.9 sq mi | 52,784 |
| 5 | Hillsborough County | 876.5 sq mi | 433,415 |
| 6 | Cheshire County | 706.7 sq mi | 78,269 |
| 7 | Rockingham County | 695.6 sq mi | 324,077 |
| 8 | Sullivan County | 537.9 sq mi | 43,961 |
| 9 | Belknap County | 401.9 sq mi | 65,147 |
| 10 | Strafford County | 367.5 sq mi | 135,043 |
By population
| Rank | Name | Population | Density |
|---|---|---|---|
| 1 | Hillsborough County | 433,415 | 494 per sq mi |
| 2 | Rockingham County | 324,077 | 466 per sq mi |
| 3 | Merrimack County | 158,078 | 169 per sq mi |
| 4 | Strafford County | 135,043 | 367 per sq mi |
| 5 | Grafton County | 93,225 | 54.6 per sq mi |
| 6 | Cheshire County | 78,269 | 111 per sq mi |
| 7 | Belknap County | 65,147 | 162 per sq mi |
| 8 | Carroll County | 52,784 | 56.6 per sq mi |
| 9 | Sullivan County | 43,961 | 81.7 per sq mi |
| 10 | Coos County | 31,343 | 17.5 per sq mi |
And the smallest
More on New Hampshire
Rebuilt from source data 30 August 2026. How these figures are produced.