1. On May 12, 1902, the Mining and Engineering Journal reported a new discovery of rich gold and silver ores in the Tombstone district of Arizona. The area had previously been one of the most profitable mining regions in the state, and this new find brought renewed interest and investment to the area.

2. In 1937, on May 12, construction of the Hoover Dam in northern Arizona was completed. The dam, which spans the Colorado River between Arizona and Nevada, was a massive engineering feat and provided much-needed electricity and water for the region.

3. May 12, 1981, saw Arizona become the first state to issue a license plate promoting organ donation. The design featured a red heart and the slogan "Legacy of Life," and has since been adopted by many other states.

4. On May 12, 1993, the Phoenix Suns basketball team won their first-ever Western Conference championship, defeating the Seattle SuperSonics in a thrilling seven-game series. The Suns would go on to face Michael Jordan and the Chicago Bulls in the NBA Finals, but ultimately lose in six games.

5. In 2008, May 12 marked the opening of the Heard Museum North in Scottsdale, Arizona. The museum is a branch of the Heard Museum in Phoenix, and focuses primarily on Native American art and culture. It features exhibits, workshops, and other educational programs.