I recently learned that map makers intentionally put fake roads, etc., into their maps to identify copyright infringements (when maps are stolen, even the errors are reproduced). These are called copyright traps. I grew up outside of Chicago near Ohare International Airport. I heard that Rand McNally once put a fake town near Ohare in their maps. I checked up on it and and found that it is true. The fake town is called Westdale and it appeared in the 1981-1983 editions of Rand McNally’s maps. Westdale is near a “Westdale Park” and a “Westdale Elementary School” (see it on google maps here).
Here is a link to more on copyright traps from the Straight Dope (the 1991 edition). This author was skeptical about the existence of the fake Chicago suburb, but it was written before google. I found the rest of the information to be interesting.