| County | Rank | Change (2020) ↓ | 2025 Pop. | 2020 Pop. |
|---|---|---|---|---|
| Carroll County | 1 | 5.07% | 52,787 | 50,240 |
| Rockingham County | 2 | 3.03% | 324,201 | 314,664 |
| Merrimack County | 3 | 3.01% | 158,679 | 154,039 |
| Strafford County | 4 | 2.84% | 134,796 | 131,074 |
| Belknap County | 5 | 2.7% | 65,495 | 63,774 |
| Cheshire County | 6 | 2.59% | 78,524 | 76,542 |
| Hillsborough County | 7 | 2.43% | 433,205 | 422,929 |
| Sullivan County | 8 | 2.2% | 44,018 | 43,069 |
| Grafton County | 9 | 2.18% | 93,181 | 91,197 |
| Coos County | 10 | -0.8% | 30,979 | 31,228 |
New Hampshire's counties show varied growth patterns from 2020 to 2025. Carroll County leads with 5.07% annualized growth, followed by Rockingham County (3.03%) and Merrimack County (3.01%). The largest counties are Hillsborough County (433,205), Rockingham County (324,201), and Merrimack County (158,679). Of the 10 counties in New Hampshire, 9 are growing while 1 has experienced population decline. Overall, counties averaged 2.53% annualized growth, with total population growing by 2.69% annually.
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