Having been to South Dakota, I'd say Maine. Seriously, their is NOTHING in SD. It isn't called 'the Badlands' because the early white folks didn't like the natives.

Well, it's late August. Where are you going? Or are you already gone?

I've never been to South Dakota.
Maine is awesome. It has virtually every kind of landscape (mountain, lake, beach, flatland). Maine has small towns, Maine has some larger towns like Portland. Plus it has great seafood. My good friend in college was from Maine, he was a very down-to-earth, fun person, to hang around with.