In “The Tommyknockers,” the alien artifact is discovered near the small Maine town of Haven.
The discovery begins when Roberta “Bobbi” Anderson, a writer of Western fiction, trips over a metal object while walking in the woods near Haven. She and her friend James Eric “Gard” Gardener excavate it and eventually realize that it is part of a vast, ancient alien spacecraft buried underground.
The ship releases an invisible influence that gradually transforms Haven’s residents. Those affected become unusually inventive, developing machines and devices far beyond their normal abilities, but they also lose judgment, empathy, and much of their humanity. The town’s isolation helps the transformation spread before outsiders understand what is happening.
Haven is easy to confuse with other fictional Maine communities in Stephen King’s work, especially Castle Rock and Derry. Those towns are important elsewhere in King’s fictional geography, but they are not the setting of the buried spacecraft in The Tommyknockers. Haven is the specific canonical answer, while the artifact itself is a protruding section of a long-buried alien vessel.