The frame story of the Sketchbook of Sir Geoffrey Crayon, Gent., the longer fictional work in which "Rip Van Winkle" appears, is that a man named Sir Geoffrey Crayon has traveled around the United States and England collecting stories from locals in different places. The opening of "Rip Van Winkle" introduces an additional frame story nested within Geoffrey Crayon's narration, that of an unreliable scholarly narrator:
The following Tale was found among the papers of the late Diedrich Knickerbocker, an old gentleman of New York, who was very curious in the Dutch history of the province and the manners of the descendants from its primitive settlers[.]
Knickerbocker documented the events of "Rip Van Winkle," and Sir Geoffrey has stumbled upon Knickerbocker's papers during his travels. Irving had formerly published a facetiously inaccurate history of New York under the pseudonym "Diedrich Knickerbocker," so Irving's dedicated readers would have immediately recognized that Sir Geoffrey was getting the story from an unreliable source.
Knickerbocker's record as a bad historian undermines the idea that "Rip Van Winkle" is factual, but it also raises questions about the extent to which factual writing is more authentic and valuable than fiction and folklore. Irving and other fiction writers at the time were trying to establish their work as a monetized profession, so it was important for people to understand that fiction held cultural value, even if it wasn't based in fact. Sir Geoffrey puts a great deal of store by the "accurate" written record Knickerbocker leaves behind:
Its chief merit is its scrupulous accuracy, which indeed was a little questioned on its first appearance, but has since been completely established, and it is now admitted into all historical collections as a book of unquestionable authority.
Sir Geoffrey further bolsters the account's authority by including, at the end of the story, excerpts from Knickerbocker's written notes. Written stories, according to Sir Geoffrey and most editors of "historical collections," become trustworthy and permanent records of historical fact once they are fact-checked.
But Knickerbocker himself relies more on hearsay than written records. Sir Geoffrey is a little suspicious about Knickerbocker's dubious methods as a historian, and yet he is inclined to trust the story's authenticity. He notes that
[Knickerbocker's] historical researches […] did not lie so much among books as among men, for the former are lamentably scanty on his favorite topics, whereas he found the old burghers, and still more their wives, rich in that legendary lore so invaluable to true history[.]
Sir Geoffrey defends Knickerbocker's reliance on oral rather than written records as a method that might better capture the "true history" of an old-fashioned community. The emphasis on the burghers' wives as the richest sources of "legendary lore" is a joke suggesting that Knickerbocker might not have been recording history so much as gossip. Like his history of New York, "Rip Van Winkle" is probably made up. Sir Geoffrey's insistence that the story is accurate suggests that the facts may not matter: this gossip, as a central part of rural culture, is "true history" even if it is made up. In addition to defending the value of folklore and local storytelling, this stance is a defense of fiction in the face of critics who called it deceitful and culturally worthless.