N.H. Rev. Stat. Ann. § 510:1

All original writs and writs of mesne process shall be served by the service date specified by the court on the summons, and shall be returnable to the superior court for Rockingham County at Brentwood; Strafford County at Dover; Belknap County at Laconia; Carroll County at Ossipee; Merrimack County at Concord; Hillsborough County at either Manchester or Nashua, as is appropriate; Cheshire County at Keene; Sullivan County at Newport; Grafton County at North Haverhill in the town of Haverhill; and Coos County at Lancaster.