Phone books. They’re thick too.
Well, sure. That's what the yellow pages basically are--advertising for local businesses. (There may be some level of listing that's free. I don't know.) As other have noted, my local yellow pages is pretty small and thin these days though with the caveat that I don't live in a city. I suspect that a listing/ad is no longer quite the requirement for local businesses that it once was.
https://en.wikipedia.org/wiki/Network_Information_Service
Jordan Hubbard has YP to thank for the infamous "rwall incident" of 1987: