Fastest Growing Counties in New Hampshire (2025)

County
Rank
Change (2020)
2025 Pop.
2020 Pop.
Carroll County15.55%53,03650,246
Belknap County22.97%65,67163,776
Merrimack County32.83%158,391154,038
Strafford County42.68%134,587131,068
Rockingham County52.6%322,801314,621
Sullivan County62.33%44,07143,068
Grafton County72.17%93,17691,198
Cheshire County82.14%78,18376,547
Hillsborough County90.98%427,076422,913
Coos County10-0.2%31,16431,227

New Hampshire County Growth Overview

New Hampshire's counties show varied growth patterns from 2020 to 2025. Carroll County leads with 5.55% annualized growth, followed by Belknap County (2.97%) and Merrimack County (2.83%). The largest counties are Hillsborough County (427,076), Rockingham County (322,801), and Merrimack County (158,391). Of the 10 counties in New Hampshire, 9 are growing while 1 has experienced population decline. Overall, counties averaged 2.41% annualized growth, with total population growing by 2.14% annually.