Jeremiah's Lot
King said in an interview that 'Salem's Lot was in part inspired by a town in Vermont called 'Jeremiah's Lot'. As I recall, he said that he was riding in rural Vermont when his companion told about the town.
From the wiki article on the novel:
In a 1969 installment of "The Garbage Truck", a column King wrote for the University of Maine at Orono's campus newspaper, King foreshadowed the coming of 'Salem's Lot by writing: "In the early 1800s a whole sect of Shakers, a rather strange, religious persuasion at best, disappeared from their village (Jeremiah's Lot) in Vermont. The town remains uninhabited to this day."[8]
Now, I believe that King is sincere: he believes the story. The problem is that there is absolutely no evidence, other than what King said that the town ever existed. It does not appear in lists of ghost towns of Vermont and there is no records I could find of any Shaker communities ever existing in Vermont.
My conclusion is that whoever told the story to King either believed it and was passing it along or was pulling his leg. share