Benedict Arnold developed interests in land and trade at Providence and Pawtuxet before settling at Newport in 1651. His knowledge of Native languages made him useful as an interpreter, although his dealings also became entangled in disputes over land and jurisdiction. At Pawtuxet he and associates placed themselves under Massachusetts authority during their conflict with Samuel Gorton.

Arnold succeeded Roger Williams as president of Rhode Island in 1657, serving until 1660 and returning in 1662. When neighboring colonies demanded action against Quakers, he defended Rhode Island's refusal to punish people merely for religious opinions, despite his own criticism of Quaker beliefs. The royal charter obtained by John Clarke in 1663 named Arnold the colony's first governor. It established a governor, deputy governor, assistants and elected deputies while protecting liberty of conscience.

He served further terms as governor in 1669–1672 and 1677–1678, dealing with competing land claims and the colony's difficult relations with Connecticut and Massachusetts. His final term followed the destruction of King Philip's War and required rebuilding colonial administration. He also retained substantial private property. His will referred to a stone-built windmill and reserved a family burial ground in Newport. He died there in June 1678 while still governor. The Revolutionary general of the same name was his great-grandson, a separate figure in the family's later history.