New York City had been founded in the 1620s by the Dutch as New Amsterdam at the southern tip of the island of Manhattan. The English conquered the territory and established the original twelve counties of the Province of New York in 1683; one of these was the City and County of New York. A 1691 law defined New York City to be the entirety of Manhattan, while Manning's Island (now Roosevelt Island), the Barn Islands (now Randalls and Wards Islands), and the Oyster Islands (now Ellis Island) were New York County. Towns had been established in the rest of the province by 1691, and were reincorporated after the American Revolution in 1788.