I have family in S.D. and they take me all over. Unfortunately Alpine is out on it's own in the boonies. There are a few really good sections where you can hit multiple breweries in a small area.
The one where Stone is has several other good breweries in the area-belching beaver, latitude 33, booze brothers, barrel harbor, iron fist, and mother earth plus a few more.
The other is further south but still 15 minutes from downtown, it has green flash, rough draft, saint archer, alesmith, hess, white labs and ballast point and a few I forgot.
I could point out some specific ones if you are looking for something particular.