I'm of a little different mindset.
1) Annual Spring horse sale in Mobridge.
2) Corn Palace Stampede (Jammie or Debey can verify if it still happens.)
3) The annual buffalo roundup and hunt.
4) A picknic in any city park in towns less then 2000.
5) Fishing at Lake Andease.
6) Evan's Plunge.
7) Badlands Baha in the early spring.
8) County fair in Armour.
9) Harvest time from Yankton to Watertown.
10) An unhurried tour of the Black Hills in "Off Season"
That, will give you a flavor of South Dakota.