Voni- I don't buy that one at all...LOTS!! of people camp fairly close to where they live. They did when I lived in KS & they sure do it here in KY. Some travel a good ways too,e.g. is the "Ohio Navy" (as they're called) that travels to Lake Cumberland,KY on the weekends. Gas stations are a possible as is anyone spotted with an RV, gun or a boat. Your asking the wrong people?
My suggestion is for people looking for a campground to ask @ places like boat,RV,tackle shop or that department in box store, gun shop, national forest offices, anything associated with the outdoors.
I have a campground guide I bought @ retirement which is the size of the NYC phone book & I never use it as the web is so much better! I will say that I've been looking for camp spots in New England & they are mostly closed after Labor Day or late Sept-virtually none in Oct! esp. after mid month. I guess they all crawl in a hole?