When we had a chance to see the Little House sites, we had to take it. First, De Smet, SD, where the Ingalls family settled after leaving Minnesota. We went to the site of their homestead, the house Pa built, and the cemetery where most of them rest. The street where the action of The Long Winter takes place was awesome - it's so WIDE! You can really see how it would have been easy to get lost in that blizzard! So neat to see in person.
And of course, Walnut Grove. The museum here was a lot of fun. The town itself is TINY, and the craziest thing - there was an Asian market there (one of the six businesses still in town) which was the ONLY place we found fresh greens (amazing Chinese mustard) in all of South Dakota, Minnesota or Iowa. People don't eat anything with chlorophyll in the midwest. We also got to go to Plum Creek and see where the dugout was. We kept an eye out for flat badgers. :) So fun!!
The rest of the time in Minnesota was spent researching family history in Madison and Marshall. Genealogy gold mine there!