Mitchell, SD is a city of about 15,000 that is 75 miles west from Sioux Falls along Interstate 90. It is somewhat of a tourist destination, mainly because of the Corn Palace:
http://en.wikipedia.org/wiki/Corn_Palace
It also has a couple museums, the Dakota Discovery Museum and the Mitchell Prehistoric Indian Village archeological site.
It has a pretty big historic downtown just south of the Corn Palace, and it didn't seem to be doing as badly as you might think (most storefronts looked occupied, though not prosperous). The first few of these were taken in the car, so I apologize for the poor quality. We didn't have time to really walk around too much.
The Corn Palace - the outside decoration is made entirely from corn.
They were redoing this side, you can see the black part looking like a paint-by-numbers code for the different colors of corn.
They have pictures of most of the previous versions of the Corn Palace, which used to be in a slightly different location, and looked pretty different. They redecorate it every year.
Has a basketball court in it