In 1823, twelve townships of Hillsborough Country – Andover, Boscawen, Bradford, Dunbarton, Fishersfield (now Newbury), Henniker, Hooksett, Hopkinton, New London, Salisbury, Sutton, and Warner – became part of Merrimack County. The town of Merrimack along the Merrimack River in south-central Hillsborough County was not included in the newly formed county to the north. Hillsborough County's administrative functions were moved from Amherst to Milford in 1866, and then to the current seats of Manchester and Nashua in 1869.
In 1823, twelve townships of Hillsborough Country – Andover, Boscawen, Bradford Dunbarton, Fishersfield (now Newbury), Henniker, Hooksett, Hopkinton, New London, Salisbury, Sutton, and Warner – became part of Merrimack County. The town of Merrimack along the Merrimack River in south-central Hillsborough County was not included in the newly formed county to the north. Hillsborough County's administrative functions were moved from Amherst to Milford in 1866, and then to the current seats of Manchester and Nashua in 1869.