The following is from Wikipedia:
Portsmouth was settled in 1638 by a group of religious dissenters from Massachusetts Bay Colony, including Dr. John Clarke, William Coddington and Anne Hutchinson. It is named after Portsmouth, Hampshire, England. Roger Williams convinced the settlers that they should go there instead of settling in the Province of New Jersey, where they had first planned on going.
It was founded by the signers of the Portsmouth Compact. Its original name was Pocasset and it was officially named Portsmouth on May 12, 1639. It became part of the Colony of Rhode Island and Providence Plantations (see Aquidneck Island) and eventually part of the State of Rhode Island and Providence Plantations, which, as of 2020, is simply the State of Rhode Island. See Portsmouth Community Videos