1. The Homestake Gold Mine began operation on July 23, 1876 in Lead, South Dakota. It would go on to become the largest and deepest gold mine in North America, producing over 40 million ounces of gold during its 125-year history.

2. On July 23, 1904, Norwegian immigrant E.T. Steen invented the first practical electromechanical speedometer while working as an engineer for the Paige-Detroit Motor Car Company in Sioux Falls. This device would become a standard feature on cars for decades to come.

3. The USS South Dakota (BB-57), a battleship named for the state of South Dakota, was commissioned on July 23, 1942. It played a key role in many Pacific Theater battles during World War II and earned 13 battle stars before being decommissioned in 1947.

4. The current South Dakota state flag was adopted on July 23, 1963. It features the state seal surrounded by a sunburst pattern on a field of blue, with the state name displayed in gold letters above the seal.

5. The first Sturgis Motorcycle Rally, which has since become a world-renowned event attracting hundreds of thousands of riders each year, was held in Sturgis, South Dakota on July 23, 1938. The rally originally consisted of a single race featuring nine participants, but has since grown to include concerts, bike shows, and other activities.