Haddonfield is a well known town amongst the horror community for being the serene suburb of Illinois where Michael Myers went on a murderous rampage. Although the movie was filmed in California and set in Illinois, the real Haddonfield is in New Jersey, and it served as the inspiration for the town's name.
Haddonfield would probably be relatively unknown town to the rest of the nation if it weren't for the film's co-writer and co-producer, the late Debra Hill, who was born there. Hill and John Carpenter worked on several films together including the first 3 Halloween movies. Hill, who at one time was romantically linked to Carpenter, grew up a mere 10 minutes away in Philadelphia, PA.
If you've been to the Monster Mania Convention in Cherry Hill, you've probably seen the signs in that area for the real Haddonfield. If you were second guessing yourself by saying "Nah, Halloween was in Illinois..." then technically you are correct, but just keep in mind that Illinois is about 700 some odd miles away from the real Haddonfield! That said, New Jersey doesn't have sour grapes about the film being set in another state because Haddonfield is already known for another monster, the Hadrosaurus Foulkii. Haddy was the first in-tact dinosaur skeleton ever found and put on display, which is friggin' cool. What town wouldn't want their own dinosaur?
Dinosaurs aside, off the top of my head, New Jersey can lay claim to Jason Voorhees, The Toxic Avenger, Vera Farmiga (Norma Bates FTW!) and the inspiration for the setting of Halloween. Knowing that so much of the basis of many classic horror films are rooted in New Jersey is pretty incredible. I think trivia like this is awesome because of how obscure it is. If you're not a big fan of the Halloween franchise, you might have been unaware of the fact that Debra Hill infused a little bit of South Jersey into Halloween.
In honor of its 35th anniversary, you can catch the original Halloween as it returns to theaters for special screenings around the country. In addition, both Halloween 4 and 5 will also be screened. Check ScreenVision.com for a full list of screenings in your area.
Other sites of interest:
Fictional Entry for Haddonfield on Horror Movies Wiki: http://horror-movies.wikia.com/wiki/Haddonfield,_Illinois
Coldwell Banker mentions the Halloween connection to NJ from a real estate perspective:
Official Site of the Hadrosaurus Foulkii: http://hadrosaurus.com
Official Haddonfield Website: http://www.haddonfieldnj.org/