Friday we took a tour of Wind Cave.  It was interesting with mostly box work formations. -- 6" fins mostly on the ceiling forming pigeon holes of various sizes.  Few other formations.  No rooms of any great size -- mostly a bunch of narrow passages.  It's the 4th longest known cave @ 137 miles of explored passages -- they say they have only explored 5 - 10% of the cave. 
   Around Rapid City S.D. the freeway is crusted with billboards.  One struck me:   "Select 55.  The Lightest Beer In The World"  --  "You'll think it's suspiciously yellow stale water"
   Further on, by the E. Vermillion River, another road-side display:  Giant painted steel hammer, flowers, fish, and curiously, a 25' tall head of Hathor, the Egyptian cow god.
   We spent the night in Mitchell home of the Corn Palace.  the Palace is  a small town arena, seating perhaps 5000 on one side of the building, with a floor area for a basketball court and a half or so, and a stage (curtained when we were there) .   Corn murals surrounding the seating, activity area.  The exterior was in the process of re-corning so we didn't see it's full splendor.
   Mitchell is also the site of the George McGovern museum.  His family doubtless cares. 
   The Spam museum is a Wonder.  As was the subsequent spam burger -- an ordinary burger, with a mighty slab of spam instead of a patty.  Perhaps too mighty, but with spam who can number the ways?  
   After the spam, we took a scenic side road (s.r. 16) for 50 miles.  In Grand Meadow we stopped and looked at a bank building:  small but very nice prairie style building.  We met an Amish buggy on the road.  From their body posture we guess the older couple in the buggy were having some issues on this particular day.  A nice side road and then back to the freeway and on to friends in Friendship.  DA