Rockingham County, New Hampshire

Rockingham County
Aerial view of Portsmouth
Location within the U.S. state of New Hampshire
New Hampshire's location within the U.S.
Coordinates: 42°57′46″N 71°04′39″W / 42.962872°N 71.077621°W / 42.962872; -71.077621
Country United States
State New Hampshire
Founded1769
Named afterCharles Watson-Wentworth, 2nd Marquess of Rockingham
SeatBrentwood
Largest townDerry
Area
  Total
795.2 sq mi (2,060 km2)
  Land695.4 sq mi (1,801 km2)
  Water99.9 sq mi (259 km2)  12.6%
Population
 (2020)
  Total
314,176
  Estimate 
(2022)
319,424
  Density400/sq mi (150/km2)
Time zoneUTC−5 (Eastern)
  Summer (DST)UTC−4 (EDT)
Congressional districts1st, 2nd
Websiterockinghamcountynh.org

Rockingham County is a county in the U.S. state of New Hampshire. As of the 2020 census, the population was 314,176, making it New Hampshire's second-most populous county. The county seat is Brentwood. Rockingham County is part of the Boston-Cambridge-Newton, MA-NH Metropolitan Statistical Area and the greater Boston-Worcester-Providence, MA-RI-NH-CT Combined Statistical Area. Per the 2020 census, it was New Hampshire's fastest growing county from 2010 to 2020.

As of 2014–2018 estimates from the American Community Survey, Rockingham County was the fourth- wealthiest county in New England, with a median household income of $90,429.