1. Statehood Day: September 16th marks South Dakota's Statehood Day. On September 16, 1889, President Benjamin Harrison signed the proclamation that officially made South Dakota the 40th state of the United States.

2. Minuteman Missile Site: On September 16, 1998, Minuteman Missile Site National Historic Site was established. This site is home to the most complete and intact military missile field of its kind, and it showcases the history of the Cold War.

3. Wounded Knee Massacre: On September 16, 1890, a tragic event took place at Wounded Knee Creek on the Pine Ridge Reservation. In what is now known as the Wounded Knee Massacre, hundreds of Lakota men, women, and children were killed by the U.S. Army.

4. Crazy Horse Memorial: On September 16, 1948, sculptor Korczak Ziolkowski began work on the Crazy Horse Memorial, which is located in the Black Hills near Custer. This ongoing project is a tribute to the Native American warrior Crazy Horse and is one of the largest mountain carvings in the world.

5. Homestake Mine: On September 16, 1983, the Homestake Mine in Lead became the first deep underground research facility in the United States. It was used for various experiments and research, including the study of neutrinos, until its closure in 2002.