The area was once within the domain of the Newichawannock Indians, an Abenaki sub-tribe which took its name from the Newichawannock River, meaning "river with many falls," now the Salmon Falls River. Their village was located at what is today Salmon Falls Village. They fished at the falls, stretching nets across the river to catch migrating salmon and other species swimming upriver to spawn. But war and disease, probably smallpox brought from abroad, decimated the native population.
Subsequently settled by about 1630, the land was part of Dover, one of the original townships of New Hampshire. The area was first called Sligo, likely after the county Sligo in Ireland, and the name survives on a town road. It would be established in 1729 as a parish called Summersworth, meaning summer town, because the ministers preached here during the summer. In 1754, it would be set off and incorporated as a town by colonial Governor Benning Wentworth, although thereafter spelled Somersworth due to a clerical error. Since the pioneers' arrival, small communities had developed near various sawmills and gristmills along the Salmon Falls River, but the center of "Summersworth" was located at Rollinsford Junction.
Beginning in the early 1820s, water powered textile mills were established at the larger falls, and the town would divide between them—Great Falls became Somersworth, and Salmon Falls became Rollinsford, incorporated in 1849. It was named in honor of the Rollins family, whose ancestor Judge Ichabod Rollins had settled there many generations before and had become the first probate judge for the state.