1. The Treaty of Fort Laramie was signed on October 27, 1868, between the United States and the Sioux Nation, which included what is now South Dakota. The treaty established the Great Sioux Reservation, which covered parts of South Dakota, North Dakota, Nebraska, and Wyoming.

2. The Rapid City Flood occurred on October 27, 1972, when a massive rainstorm caused flooding and landslides in Rapid City and the surrounding areas. The disaster claimed the lives of 238 people and caused over $160 million in damages.

3. On October 27, 1975, the Crazy Horse Memorial in the Black Hills of South Dakota was dedicated. The memorial is a massive monument to the Lakota warrior Crazy Horse, with a goal of portraying the Native American perspective in the storytelling of American history.

4. The state bird of South Dakota, the ring-necked pheasant, was first introduced to the state on October 27, 1908. The birds were brought from China and released in the Winner area, and soon spread throughout the state becoming a favorite game bird among hunters in South Dakota.

5. On October 27, 1949, the South Dakota School of Mines and Technology officially became a university. The institution had been founded in 1885 as the Dakota School of Mines and initially offered programs in mining engineering and related fields. Today, South Dakota Mines offers a wide range of engineering, science, and technology programs.