1. On December 20, 1864, a group of ten soldiers from the United States Army were killed in an ambush by Apache warriors in the Salt River Canyon. This event came to be known as the Battle of Salt River Canyon, and was one of many clashes between settlers and Native American tribes during Arizona's territorial period.

2. In 1912, December 20 marked the day that Arizona officially became the 48th state in the Union. This momentous occasion was marked by a series of celebrations and ceremonies throughout the state, including parades, fireworks, and speeches by local politicians.

3. On December 20, 1943, the United States Army Air Forces established the Williams Air Force Base in Chandler, Arizona. The base was used as a training facility for pilots during World War II, and continued to operate until it was decommissioned in 1993.

4. In 1972, Arizona State University's Sun Devil Stadium hosted its first ever Fiesta Bowl on December 20. The game featured Arizona State University and the University of Pittsburgh, with Arizona State emerging as the victor in a thrilling 28-7 win.

5. 2019 marks the 131st anniversary of the founding of the Arizona Republic, one of Arizona's oldest and most respected newspapers. Though the paper has undergone many changes throughout its history, including several mergers and acquisitions, it remains an important voice in the state's media landscape.