
Hillsborough County
- State:
- New Hampshire
Hillsborough County's estimated 2025 population is 427,076 with a growth rate of -0.03% in the past year according to the most recent United States census data. Hillsborough County is the 1st largest county in New Hampshire. The 2010 population was 401,064 and has seen a growth of 6.49% since that time.