South Dakota was the 40th state to enter the union. North and South Dakota both became states on November 2, 1889. President Benjamin Harrison signed the documents without knowing which was signed first. Since North Dakota comes first alphabetically, it is said to be 39th and South Dakota is 40th.

South Dakota's capital is Pierre (pronounced Peer.) Pierre is named after Fort Pierre. Fort Pierre was named for Pierre Choteau, Jr., president of the American Fur Company.