Much of small town America has some sort of free camping, if you'll ask locals. So I always ask. Sometimes it's a city park, or the bank of the river outside of town, or some little lake behind a hill. Locals need a place to camp, fish and picnic, right? And they aren't going to pay for it. So there often is an unoffical campground that's often better than the ones you have to pay for. Just ask about it at the local mini-mart. Your local Baptist Church is even a better bet.
The only trouble I've really had with the *locals only* camping spots is with drunk teenagers. But most of the time they get lost if you threaten to tell their folks.........