Tree Trimming in Southold, NY.

Algonquian-speaking tribes, related to those in New England across Long Island Sound, lived in eastern Long Island before European colonization. The western portion of the island was occupied by bands of Lenape, whose language was also one of the Algonquian languages.

In surrounding areas, the Dutch colonists had established early settlements to the northwest: on the upper Hudson River was Fort Orange, founded in 1615 (later renamed Albany by the English); and New Amsterdam (later renamed Manhattan) in 1625. Lion Gardiner established a manor on Gardiners Island in East Hampton in 1639. Just across from Long Island, the Connecticut Colony, or Connecticut River Colony, was established in 1636. The Puritans established New Haven Colony separately in 1638, even though it was largely surrounded by Connecticut Colony. New Haven Colony was a theocracy, governed only by church members.

English Puritans from New Haven Colony settled in Southold on October 21, 1640. They had purchased the land in the summer of 1640 from the group of Indians related to the Pequot of New England, who lived in the territory they called Corchaug (now Cutchogue). Settlers spelled the Indian name of what became Southold as Yennicott. In most histories Southold is reported as the first English settlement on Long Island in the future New York State. Under the leadership of the Reverend John Youngs, with Peter Hallock, the settlement consisted of the families of Barnabas Horton, John Budd, John Conklin, John Swazy, William Wells, John Tuthill, and Matthias Corwin.