When I first started RVing, I googled "(State name) Tourism" for the states I intended to drive through. I eventually saved a list of all the continental US states' tourism sites. Some states are better than others, but they all have an economic interest in tourism. South Dakota's is one of the best.
Then, as I entered a state, I stopped in the first expressway rest area. They all have a wall full of tourist attraction folders. I ask the folks working behind the desk at the rest area for their favorites. And its a good chance to ask about current road conditions and stretch your legs.
P.S. Feel free to skip Ripley's Believe It or Not.