In the spring of 1636 Williams and a number of his followers from Salem began a settlement on land that Williams had bought from Massasoit, only to be told by Plymouth that he was still within their land grant. They warned that they might be forced to extradite him to Massachusetts and invited him to cross the Seekonk River to territory beyond any charter. The outcasts rowed over to Narragansett territory, and having secured land from Canonicus and Miantonomi, chief sachems of the Narragansetts, Williams established a settlement with twelve "loving friends". He called it "Providence" because he felt that God's Providence had brought him there. (He would later name his third child, the first born in his new settlement, "Providence" as well.) He said that his settlement was to be a haven for those "distressed of conscience", and it soon attracted quite a collection of dissenters and otherwise-minded individuals.
From the beginning, the settlement was governed by a majority vote of the heads of households, but "only in civil things", and newcomers could be admitted to full citizenship by a majority vote. In August 1637 they drew up a town agreement, which again restricted the government to "civil things". In 1640, another agreement was signed by thirty-nine "freemen", (men who had full citizenship and voting rights) which declared their determination "still to hold forth liberty of conscience". Thus, Williams had founded the first place in modern history where citizenship and religion were separated, a place where there was religious liberty and separation of church and state.
In November 1637, the General Court of Massachusetts disarmed, disenfranchised, and forced into exile the Antinomians, the followers of Anne Hutchinson. One of them, John Clarke, learned from Williams that Aquidneck Island might be purchased from the Narragansetts. Williams facilitated the purchase by William Coddington and others, and in the spring of 1638 the Antinomians began settling at a place called Pocasset, which is now the town of Portsmouth, Rhode Island. Some of the Antinomians, especially those described by Governor John Winthrop as "Anabaptists", settled in Providence.
In the meantime, the Pequot War had broken out, and it was a great irony that Massachusetts Bay was forced to ask for Roger Williams' help. He not only became the Bay colony's eyes and ears, he used his relationship with the Narragansetts to dissuade them from joining with the Pequots. Instead, the Narragansetts allied themselves with the English and helped to crush the Pequots in 1637-1638. When the war was over, the Narragansetts were clearly the most powerful Indian nation in southern New England, and quite soon the other New England colonies began to fear and mistrust the Narragansetts. They came to regard Roger Williams' colony and the Narragansetts as a common enemy. In the next three decades Massachusetts, Connecticut, and Plymouth exerted pressure to destroy both Rhode Island and the Narragansetts.