They fished at the falls, stretching nets across the river to catch migrating salmon and other species swimming upriver to spawn.

An historical marker on Sligo Road reads, "Near this place lived David Hamilton of Westburn born in the parish of Cambuslang, Scotland in October 1620; captured by Oliver Cromwell at the Battle of Worcester, England, September 3, 1651; Brought to America as a prisoner in chains on the "John and Sarah" in the same year; settled near here and married Annah Jaxson of Lanark, Scotland.

In 1754, it was set off and incorporated as a town by colonial governor Benning Wentworth, although thereafter spelled "Somersworth" due to a clerical error.

Since the first settlers' 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.

As part of their expansion, the town was laid out in an easy-to-navigate grid plan, with the three-story boarding houses and an adjoining mill building made of brick to withstand fires.

[7] The town thrived into the first decades of the 20th century and eventually became home to many immigrant families whose forebears came to work in the mills.

Although the town planners originally forbade the mill workers to drink alcohol and required that they attend church on Sunday, during Prohibition, its proximity to temperate Maine and the Boston & Maine Railroad line led to the establishment of numerous bars and a relatively short-lived but racy reputation for free-flowing liquor.

The western half of the town is drained by Rollins and Twombly brooks, which flow south to the Cochecho River in neighboring Dover.

Garrison Hill, 290 feet (88 m) above sea level, occupies the town's border with Dover to the west.