The fictional Maine town featured in Stephen King's Needful Things and The Dark Half is Castle Rock.
Castle Rock is one of the central locations in King's fictional Maine geography. It first appeared in The Dead Zone (1979) and later became the setting for novels, novellas, and short stories including Cujo, The Dark Half, Needful Things, and The Sun Dog.
King based Castle Rock partly on his hometown of Durham, Maine, while the name comes from the mountain fortress in William Golding's Lord of the Flies. In Needful Things, the town has roughly 1,500 residents and becomes the target of Leland Gaunt's supernatural manipulation.
Castle Rock is often confused with King's other fictional Maine towns: Derry, the setting of It, and Jerusalem's Lot, the setting of 'Salem's Lot. Chester's Mill, meanwhile, is the town sealed off in Under the Dome. Needful Things was promoted as the 'Last Castle Rock Story,' although King later returned to the town in additional fiction.