Hi L-Bunny, I did southern SD and southern MN in 08. I grew up in Jackson MN and our route was south of I90 the entire way. The Root River Trail in the SE corner of MN was great; Spam Museum in Austin a must stop; and small rural towns with County roads with little traffic. Our route is blogged at: http://www.fllt.org/blog/
Read days 35-46. Most may consider the route less than spectacular because it is a " rural plains culture trip". We were traveling west to east and those 2 states ( and 2 days in Iowa) were our last vestiges of the "west" (live in NY now)
If you want more details than the blog has let me know.