1. In 1862, the largest Indian massacre in American history occurred in southwestern Minnesota, but it also affected parts of what is now South Dakota. The conflict, which became known as the Dakota War of 1862, lasted for six weeks and resulted in the deaths of hundreds of Native Americans, settlers and soldiers.

2. On May 12, 1880, the town of Lead, South Dakota was officially incorporated. Lead was founded in the 1870s as a mining town, and its name comes from the lead ore that was extracted from the area.

3. On May 12, 1898, the Spanish-American War began, with South Dakota being one of the first states to offer troops for the conflict. The 1st South Dakota Volunteer Infantry Regiment fought in several battles, including the Battle of San Juan Hill in Cuba.

4. In 1930, the presidents of the United States and Mexico met at the border town of Nuevo Laredo, which is located just south of South Dakota. President Herbert Hoover and Mexican president Pascual Ortiz Rubio discussed issues related to trade and border security.

5. On May 12, 1990, the state of South Dakota passed the nation's first statewide smoking ban, prohibiting smoking in all public buildings, including restaurants and bars. The law was controversial at the time, but has since been adopted by many other states and cities across the country.