Jefferson Park, Florida
Jefferson Park is "a massive subdivision, because that's what Florida does with land" (Prologue.2). There doesn't seem to be anything remarkable about it at all. When Quentin and Margo Roth Spiegelman find a dead man, Margo wonders "Maybe it was drugs" (Prologue.18), because when a Florida man ends up dead, it's usually drugs.
This town could basically be any suburb. What matters is how the characters feel about it. Quentin doesn't mind suburban life, but Margo hates it—she considers it a paper town (check out "What's Up with the Title?") and decides to leave.
Margo flees Jefferson Park to Agloe, New York. Don't try typing it into Google Maps, though, because it won't pop up. Agloe is "a fictitious village created by the Esso company in the early 1930s and inserted into tourist maps as a copyright trap, or paper town" (2.20.40). Cool trick. And since Margo seems to be unhappy wherever she goes, she goes somewhere that doesn't exist. We guess that way she can't be unhappy with it?
When Quentin tracks her down, she still can't believe that he'd want to go back to Jefferson Park. He agrees that the people are kind of weak there, but the place is fine. She counters, "The people are the place is the people" (3.22.88). Deep stuff.
Do you believe that? And if so, does that make Margo a paper town, too? Is she a copyright trap? A construct to trick people? And if Margo Roth Spiegelman settles down in a paper town, does that mean she doesn't exist either? It's like trying to figure out the sound of one hand clapping.