Green Bay to Sturgis, what's the best scenic route?

[Eddie Haskell]

The wife and I are going to ride out to the Dakota's this summer, not going to "Sturgis" but out that direction (Neenah, WI to Sundance, WY). I have an Ultra, the wife a Sportster, she insists on riding her own bike so I'm thinking if we take a slow leisurely back roads route the fact that she's on a Sporty shouldn't matter as much. You get the idea, the plan is to ride 5-6 hours a day and we have a 8-9 day vacation planned. I'm sure there are some great roads to ride that could easily be overlooked, any help would be appreciated.

[dano32]

I make this trip sometimes twice a year...(mother in law lives in Rapid City) If i had time i would go up threw wisconsin and then cut over thru Mn.
the interstate is not that great thru MN. all flat and no trees...
Dan