Just saw this interesting site about the history of pizza.http://members.aol.com/GLilli/piz.html
It claims that chicago deep dish is a purely americanized version.
When I was growing up, all I knew was New York style which everybody claimed was neapolitan and sicilian which was basically the same only with a thick square crust. If you look around the net, you'll also find calabrian, genovese and venetian pizza.
My first experience with thin crust came with the advent of Pizza Hut and their dough rolling machines