1. In 1864, the first US military post was established in the Dakota Territory at Fort Sully, located on the Missouri River. It was named after General Alfred Sully, who was responsible for many of the military campaigns against the Dakota Sioux in the 1860s.

2. On February 26, 1891, the South Dakota Capitol Building was completed in Pierre. The building was designed by architect George R. Mann and features a central dome, Corinthian columns, and a granite exterior. It is listed on the National Register of Historic Places.

3. In 1913, the first automobile bridge across the Missouri River was opened in Yankton, South Dakota. The bridge was built by the Yankton Bridge Company and cost $270,000 to construct. It was a major improvement over the ferry service that had previously been used to cross the river.

4. On February 26, 1962, the US Air Force launched a Titan II missile from its base at Ellsworth Air Force Base in South Dakota. The missile was part of the US nuclear arsenal during the Cold War and was capable of delivering a nuclear warhead to targets thousands of miles away.

5. In 1980, the abandoned mining town of Lead, South Dakota, made headlines when a fire broke out in the nearby underground Homestake Mine. The fire burned for several weeks, and it was eventually extinguished by pumping water into the mine. The mine was permanently closed in 2002, but it remains an important site for scientific research in fields such as physics and astrophysics.