Madison, WI to Badlands and back - best route?

We live just north of you in Baraboo, WI. We went to Theo Roosevelt NP last summer and had a good time. However, it does add almost 400 miles to your trip and 3 days minimum.
If you don't have the time for that, you may want to take highway 14 either out or back. It is a good road with minimal traffic. The little towns are fun to stop at and the people are very nice.
I do not enjoy driving on the interstate so US and state highways are my preferred routes. I am usually not in a hurry.