1. The Battle of the Little Bighorn occurred on December 5, 1876. This historic battle took place in Montana but had a significant impact on South Dakota, as it marked the beginning of the end of Sioux resistance to white settlement of the region.

2. On December 5, 1889, South Dakota became the 40th state to join the Union. This event marked the culmination of years of effort by Dakota Territory residents who had long sought statehood.

3. In 1927, the iconic Mount Rushmore National Memorial was dedicated on December 5. The massive sculpture features the faces of four U.S. presidents - George Washington, Thomas Jefferson, Abraham Lincoln, and Theodore Roosevelt - carved into a granite mountain in the Black Hills.

4. On December 5, 1979, an oil drilling rig owned by the Gulf Oil Corporation exploded in the waters off the coast of Galveston, Texas. The disaster resulted in the largest oil spill in U.S. history at the time, and the cleanup effort involved many South Dakota-based companies.

5. Finally, on December 5, 2007, South Dakotan Tim Johnson announced that he would not seek re-election to the U.S. Senate. This decision set off a heated political battle to succeed him, with a number of high-profile candidates entering the race over the following months.