1. The Homestake Mine strike began on July 21, 1934, in Lead, South Dakota. It was a six-month-long strike over wages and working conditions, which resulted in violence and the involvement of the National Guard.

2. The Battle of Wounded Knee began on July 21, 1890. It was a tragic event in which approximately 300 Lakota Sioux men, women, and children were killed by the U.S. Army.

3. George McGovern was born on July 21, 1922, in Avon, South Dakota. He served in the U.S. Senate and was the Democratic Party's nominee for President in the 1972 election.

4. On July 21, 1960, the first Titan missile was tested at the Ellsworth Air Force Base in South Dakota. The Titan was one of the largest land-based intercontinental ballistic missiles ever developed by the U.S. military.

5. July 21, 1923, marked the dedication of Mount Rushmore. President Calvin Coolidge delivered a speech at the event, which celebrated the completion of the first stage of the monument's construction.