1. The Battle of the Big Hole occurred on December 23, 1876.
On this day, a group of Nez Perce Native Americans engaged in a battle with the United States Army in Montana, not far from the Wyoming border. The Nez Perce were trying to escape to Canada in order to avoid being forced onto a reservation. The battle was a significant loss for the Nez Perce and is seen as a critical moment in the history of the Indian Wars.

2. The National Elk Refuge was established on December 23, 1912.
This refuge is located just south of Jackson, Wyoming, and covers approximately 25,000 acres. It was established to provide a protected habitat for elk and other wildlife that migrate to the area during the winter months.

3. The first Department of Anatomy and Physiology was established in Wyoming on December 23, 1920.
This department was created at the University of Wyoming and was an essential step in the development of the university's medical school.

4. Cheyenne was started on December 23, 1867.
Cheyenne was established as a stop on the Union Pacific Railroad and has since grown to become the capital city of Wyoming.

5. The Wyoming State Hospital was established on December 23, 1886.
This hospital was established to provide care and treatment to individuals with mental health conditions. The hospital is still in operation today and provides a range of care services to individuals throughout Wyoming.