We're planning a 5 week trip in Sept. also. Leaving day after Labor day from Va, and planning 10 days out to SD to see the sights, including all that everyone has mentioned, Devil's Tower thrown in. Plan on 10 days in the area, then cutting across the northern states eastbound to the Michigan UP, then down the lakeside.
Plan to stay a J Bar as following posts, seems to be a great park/base.
Definately following this thread.
Steve & Cheryl + Charlie & Casey, our furry kids.
2012 Forrest River Lexington 283ts
Toad, 2013 Subaru XV Crosstrek
Camping trips this year so far...8