1. On April 15, 1991, the Arizona Diamondbacks were officially unveiled as Major League Baseball's newest expansion team. This marked the beginning of a new era for sports in Arizona, and the start of a successful franchise that would go on to win the World Series in 2001.

2. April 15, 1952, marks the date of the deadliest plane crash in Arizona's history. An Air Force transport plane carrying 44 passengers and crew members crashed into a mountain near Kingman, killing everyone on board. The tragedy remains a somber reminder of the risks associated with air travel and the sacrifices made by those serving in the military.

3. April 15, 1912, was the date of the sinking of the Titanic. While this event occurred thousands of miles away, it had a significant impact on the residents of Arizona, many of whom lost loved ones in the disaster.

4. On April 15, 1862, the First Battle of Picacho Peak took place during the American Civil War. This small engagement marked the westernmost battle of the war and was a significant event for Arizona, which was not yet a state at the time.

5. April 15, 1960, marked the opening of the Phoenix Zoo. The zoo has become one of the most popular attractions in the state and is home to over 3,000 animals from around the world. The opening of the zoo was a significant milestone for Arizona, as it helped to establish the state as a destination for tourism and recreation.