I am in the process of planning a trip for June 2014. We would fly into Minneapolis and stay a couple days to see MOA. We then would like to visit Walnut Grove, DeSmet, and go all the way to Rapid City, SD. I priced one way car rentals from Minneapolis to Rapid City and the price is outrageous. I am thinking that maybe it would be cheaper to rent in Minneapolis and drop off near Walnut Grove or in a city right before hitting Sioux Falls, SD. Can anyone tell me where the last major city is before hitting South Dakota that would have car rentals? I'm not having much luck on my own. Thanks so much in advance. We are trying to take the kids to see all 50 states. Any suggestions are appreciated.