1. The Black Hills Gold Rush began on September 17, 1874, when a group of prospectors led by General George Armstrong Custer discovered gold in the Black Hills of South Dakota. This discovery sparked a rush of settlers and miners to the area, which was still considered to be Native American land. The resulting conflict eventually led to the Battle of the Little Bighorn in 1876.

2. The South Dakota State Capitol building was dedicated on September 17, 1910. The building, located in Pierre, features a central dome that rises 165 feet above the ground and is covered in 18-karat gold leaf. It is considered one of the most impressive state capitol buildings in the United States.

3. On September 17, 1936, the Rural Electrification Administration (REA) was established by President Franklin D. Roosevelt. This federal agency was tasked with bringing electricity to rural areas of the United States, including many parts of South Dakota. The REA helped to modernize and improve the lives of millions of Americans who previously had no access to electric power.

4. The Sturgis Motorcycle Rally, one of the largest motorcycle gatherings in the world, began on September 17, 1938. The rally is held annually in Sturgis, South Dakota, and attracts hundreds of thousands of bikers and spectators from around the world. The event includes concerts, motorcycle races, and a wide range of other activities.

5. The United States Air Force Academy was established on September 17, 1954. The academy, which is located just outside of Colorado Springs, Colorado, has produced thousands of officers for the United States Air Force. Many of these officers have gone on to achieve high ranks and lead important military operations, including several who have served as astronauts.