1. On December 15, 1817, Wisconsin became a part of the Michigan Territory. This marked the beginning of Wisconsin's territorial period, which lasted until statehood in 1848.

2. On December 15, 1862, the Battle of Prairie Grove took place in Arkansas during the Civil War. Many Wisconsin soldiers fought in this battle as part of the Union army.

3. December 15, 1906, is the birthdate of Oscar Mayer, the founder of the Oscar Mayer Company in Madison, Wisconsin. The company is famous for its hot dogs, bologna, and other meat products.

4. On December 15, 1910, Wisconsin Superior High School defeated Racine High School in the first state basketball championship game. Today, the state basketball tournament is one of the most popular events in Wisconsin sports.

5. December 15, 1960, marks the unveiling of the world's largest fiberglass statue, the "Hodag," in Rhinelander, Wisconsin. The Hodag is a mythical creature said to roam the Northwoods of Wisconsin and is now a beloved symbol of the region.