1. In 1894, the Tempe Normal School (now Arizona State University) held its first ever winter commencement ceremony on December 18. Seven students received their diplomas in front of a crowd of approximately 300 people.

2. On December 18, 1912, President William Howard Taft signed a proclamation admitting Arizona and New Mexico as states into the United States. This made Arizona the 48th state of the nation.

3. The Flamingo Hotel and Casino in Laughlin, Nevada opened on December 18, 1988. The hotel was significant in Arizona history because it was the first casino in Laughlin to have a south-of-the-border theme, which proved to be a popular draw for many Arizonans.

4. In 2001, the Arizona Diamondbacks signed free agent pitcher Curt Schilling to a three-year, $32 million contract on December 18. Schilling went on to help lead the Diamondbacks to their first ever World Series championship in 2001.

5. December 18, 2012 was a significant day in Arizona history because it marked the first time in 35 years that the state recorded no executions. This was due in part to a nationwide shortage in lethal injection drugs, which made it difficult for states to carry out death sentences.