English explorer Henry Hudson became the first European to see this area in 1609, opening the way for Dutch, Swedish, and English settlers in the Delaware Valley, which was named for Lord de la Warr, governor of the Virginia colony. In 1681, King Charles II granted William Penn the right to found the colony of Pennsylvania, including present-day Thornbury. Penn, a pacifist Quaker, hoped to create a place where people could practice democracy and religious tolerance, and he quickly sold large parcels of land to people who became known as First Purchasers. George Pearce was a First Purchaser in this area, and because his wife was from Thornbury, Gloucestershire, England, that is the likely origin of Thornbury's name. That same year Penn sold land that became Thornbury for 100 pounds per 5,000 acres; in 1685 John Beller purchased land for Locksley Grist Mill, which operated from 1701 to 1938, and in 1687 Thornbury Township was officially incorporated.