 In 1662 Arnold was once again elected president of the colony , and in the second year of this term , the result of Clarke 's earlier diplomacy came to fruition with the Royal Charter of 1663 , which historian Thomas Bicknell described as " the grandest instrument of human liberty ever constructed . " Under this instrument Arnold became the first governor of the Colony of Rhode Island and Providence Plantations , with William Brenton as his Deputy . The earlier governing body , the Court of Commissioners , was replaced with a legislature of ten Assistants and a House of Deputies , with six from Newport , and four each from Providence , Portsmouth and Warwick . One of the first acts performed by Arnold as governor was to address a letter to Governor Winthrop of Connecticut about running a line between the two colonies as provided by the Charter . In 1664 the King 's Commissioners came to Rhode Island to settle claims of jurisdiction over the Narragansett country , specifically addressing rival claims between the Rhode Island and Connecticut colonies over land at Westerly and the settlement at Wickford . While the commissioners were able to forestall a major confrontation , no substantial changes were made , and the disputes between the two colonies would continue for the next fifty years . The King 's Commissioners also appointed Arnold as a justice of the peace and a magistrate of the " King 's Province " ( later Washington County , Rhode Island ) . 
