Exploring is the finest way to vacation. I head out without destination and find the most beautiful spots imaginable. I like pulling up for the night in the woods, at fishing access sites and public access around dams and rural "Park 'n' Ride" lots. Here in Michigan, hunters develop and maintain thousands of camping locations, usually a simple "two-track" that leaves and rejoins maintained roads. These are often only 50 feet or so long and unsed for most of the year. Dead-end roads are great, often caused when interstates were built. Usually surrounded by farmland or woods, these places get little traffic, yet are maintained and easy to find.
If you belong to VFW, Moose or similar orgs, ask about overnight parking.. These are great when there is a dance or social evevt (Steak night, BBQ, or Friday Fish Fry) going on. Call ahead, or arrive and ask around.
Use your imagination. No need to chase campground slots. Do not overlook scenic view sites, historical marker pullouts and rest areas along old highways that were bypassed by freeways 50 years ago. Many still exist, about 50-60 miles apart.