1. The Summer Solstice: June 21 marks the beginning of summer and the longest day of the year. In South Dakota, this means the sun will be up for approximately 15 hours and 41 minutes.

2. Native American Day: In 1990, Governor George S. Mickelson declared the second Monday in October as Native American Day. However, some Native American tribes in South Dakota celebrate this day on June 21 to coincide with the Summer Solstice.

3. Great Flood of 1972: On June 21, 1972, heavy rainfall led to flooding throughout the state. The floodwaters were so severe that some towns were completely submerged, and the National Guard was called in to assist with rescue efforts.

4. Father's Day: Although Father's Day is celebrated on the third Sunday in June across the United States, it is still an important day in South Dakota. Many families gather to celebrate and honor their fathers on this day.

5. Wild Bill Hickok's Death Anniversary: On June 21, 1876, Wild Bill Hickok was shot and killed while playing poker in Deadwood, South Dakota. His death is still commemorated in the town's annual Days of '76 celebration.