1. On May 11, 1880, the town of Deadwood was incorporated. The town became famous for its gold rush in the late 1800s and early 1900s, and was once home to notorious figures such as Wild Bill Hickok and Calamity Jane.

2. On May 11, 1961, the Custer State Park Buffalo Roundup was officially approved by the South Dakota Game, Fish and Parks Commission. This annual event has been taking place since 1965 and attracts thousands of visitors each year to watch cowboys and cowgirls round up the park's buffalo herd for health checks and other management purposes.

3. May 11, 1978, saw the groundbreaking ceremony for the Mount Rushmore National Memorial Visitor Center. The center was officially opened in 1998 and serves as a hub for visitors to learn about and explore the iconic sculpture carved into the Black Hills.

4. The first flight of the South Dakota Air National Guard's F-16 Fighting Falcon aircraft took place on May 11, 1983. The F-16 has been an important part of the state's military history, and the South Dakota Air National Guard continues to operate the aircraft today.

5. On May 11, 1992, the Pine Ridge Indian Reservation was declared a federal disaster area due to flooding caused by heavy rains. The flood destroyed homes and businesses and caused millions of dollars in damages, but in the wake of the disaster, the people of Pine Ridge came together to rebuild and support one another.