I'm from New York, so let's be real about what I think a small town is. Trust me, it's not small. I spent one night in Custer, SD. It's a town with two stoplights that looked like it came right out of the movie Cars. However, it was quaint. The people were so sweet. And I had the best burger I have ever eaten in my life at Sage Creek Grille. (I went buffalo burger because when in rancher country . . .)
I missed Keystone, a sleepy town just outside of Mt. Rushmore, due to time constraints, and I have regretted not going back. Build in the time. Stop in the small towns.