Rockingham County is located in the southeastern part of the state. The county seat is Brentwood. The population in 2000 was 277,359. The largest towns are Derry, Salem, and Londonderry. Rockingham is bordered by Strafford County to the north, the Atlantic Ocean to the east, the State of Massachusetts to the south, and Merrimack and Hillsborough Counties to the west.- Category ID : 294625