When you get to Minneapolis, hit the Mississippi river roads and follow it south all the way to Wabasha, MN then cross into Wisconsin @ Nelson, WI and head east from there. after Red wing, MN is where the road gets really good going south.
Beautiful road, and very very popular with bikes. Its a must ride road for the state.
Check out the route on google maps, to know the best route down. (sorry not good with road numbers)
I think MN has more miles right next to the river than sconi does, but you MUST stop @ nelson cheese in nelson, wi. Great Ice cream, great sandwiches, great cheese, its an all around great stop. It is filled with bikes in the summer months.