The Town of Brookhaven is one of the ten towns into which Suffolk County, New York, United States, has been divided. Part of the New York metropolitan area, it is located in central Suffolk County and is the only town in the county that stretches from the North Shore to the South Shore of Long Island. The population of the town was 486,040 at the 2010 census. It is the largest of the 932 towns (by area, if including water area) in the state of New York, and the second most populous, exceeded only by the town of Hempstead in Nassau County.
The first known inhabitants were Algonquian-speaking Native Americans, of the Setauket and Unkechaug tribes. The first English settlers arrived around 1640, and in 1655, several purchased Brookhaven's land from its tribal inhabitants. Early English settlers farmed, fished, and hunted whales.
The first English settlement was named Setauket after the native American tribe. In 1666, Governor Richard Nicolls granted a patent for the town which confirmed title to the lands purchased, and permitted additional purchases. Governor Thomas Dongan issued a patent in 1686 which granted powers to the town and established a representative form of government.
The letter "D" on the official seal, associated with the original Dongan patent officially establishing Brookhaven, is a cattle branding letter assigned to Brookhaven in the mid-17th century, along with whaling harpoons.