1. On January 21, 1972, the Oglala Sioux Civil Rights Organization declared war against the United States government in what is now known as the Wounded Knee Incident. The 71-day armed conflict resulted in the deaths of two Native Americans and one federal agent.

2. On this day in 1984, South Dakota Governor Bill Janklow signed a bill making South Dakota the first state to officially celebrate the birthday of civil rights leader Martin Luther King Jr. as a state holiday.

3. In 1903, the first statewide meeting of South Dakota's Federation of Women's Clubs was held on January 21 in Sioux Falls. The organization played a key role in advocating for women's suffrage and other social reforms in the early 20th century.

4. On January 21, 1943, the US Army Air Force established the Rapid City Army Air Base, later known as Ellsworth Air Force Base. The installation played a crucial role in the Cold War, and today is home to B-1 bombers and other strategic aircraft.

5. January 21, 1986, was a historic day for South Dakota's tourism industry, as the state opened its first casino in Deadwood. The move sparked a wave of gambling-based development in the town, helping to revive its economy and attract millions of visitors annually.