1. Statehood Day: May 17 marks the anniversary of the day South Dakota was admitted into the Union as the 40th state in 1889. It is celebrated every year as Statehood Day and is recognized as a legal holiday in the state.

2. First Female Governor: On May 17, 1993, South Dakota made history by electing its first female governor, Republican Christine Todd Whitman. She served as governor until 2001 and went on to become the head of the U.S. Environmental Protection Agency under President George W. Bush.

3. Homestake Gold Mine: The Homestake Gold Mine in Lead, South Dakota is one of the deepest and largest gold mines in the United States. On May 17, 1876, George Hearst purchased the mine for $70,000 and turned it into one of the most profitable gold mines in the country.

4. Mount Rushmore: Although construction on Mount Rushmore began in 1927, May 17, 1929 marked the official start of work on the iconic monument. The faces of Presidents George Washington, Thomas Jefferson, Theodore Roosevelt, and Abraham Lincoln were all carved into the granite over the course of 14 years.

5. Randy Johnson's Perfect Game: On May 17, 1994, Arizona Diamondbacks pitcher Randy Johnson threw a perfect game against the Atlanta Braves at Turner Field in Atlanta. It was the first perfect game in Diamondbacks history and the 15th in major league baseball history.