1. Statehood Day - On October 11, 1889, South Dakota officially became the 40th state in the United States of America. This is why October 11 is celebrated as Statehood Day in South Dakota.

2. Black Hills Gold Rush – The discovery of gold in the Black Hills in 1874 led to a massive influx of settlers and miners over the next few decades. This event is significant to South Dakota's history as it marked the beginning of the state's economic growth.

3. Flood of 1965 – On October 11, 1965, a severe precipitation event occurred in the Black Hills region of South Dakota, resulting in devastating flash floods. Over 200 people were killed, and the area suffered immense damage. This natural disaster led to major changes in the state's disaster response and prevention protocols.

4. Mount Rushmore Dedication – The iconic Mount Rushmore National Memorial was dedicated on October 11, 1927. The monument features the 60-foot tall faces of four U.S. presidents: George Washington, Thomas Jefferson, Theodore Roosevelt, and Abraham Lincoln. It has become a major tourist attraction in South Dakota and is one of the most recognizable landmarks in the world.

5. Crazy Horse Memorial – On October 11, 1948, sculptor Korczak Ziolkowski began work on the Crazy Horse Memorial, a massive sculpture that still remains in progress today. When completed, it will be the world's largest mountain carving and will depict the Oglala Lakota warrior Crazy Horse on horseback. This ambitious project is a significant cultural site for Native Americans and has become another popular tourist destination in South Dakota.