1. In 1858, the Yankton Sioux Treaty was signed between the United States and the Yankton Sioux tribe in present-day South Dakota. The treaty established a reservation for the tribe and attempted to promote peaceful coexistence between the two groups.

2. On August 9, 1876, a skirmish occurred between Lakota Sioux and a group of soldiers led by Captain James Powell near Slim Buttes in western South Dakota. The Lakota, led by Chief American Horse, were able to repel the attack and inflict numerous casualties on the soldiers.

3. The town of Mitchell, South Dakota was founded on August 9, 1879. The town is named after Alexander Mitchell, a Wisconsin senator and railroad executive who played a key role in the expansion of railroads in the western United States.

4. On August 9, 1890, the Battle of Wounded Knee Creek occurred between the United States Army and the Lakota Sioux. The battle marked the end of the Indian Wars and resulted in the deaths of over 150 Lakota, including women and children.

5. In 1945, South Dakota native and war hero Joe Foss was awarded the Medal of Honor for his service as a Marine Corps fighter pilot in World War II. Foss shot down 26 enemy planes and was credited with numerous other victories during his service. He later went on to serve as governor of South Dakota.