1. AZ Highway 87 Opened: On May 18, 1956, a section of Arizona State Route 87, also known as the Beeline Highway, was opened for traffic. The highway now stretches over 130 miles connecting Phoenix to Payson, and is known as one of the most scenic routes in the state.

2. Flagstaff Is Chartered: On May 18, 1894, Flagstaff, Arizona was officially incorporated and chartered as a city. Today, Flagstaff is known as the gateway to the Grand Canyon and is home to Northern Arizona University.

3. Arizona State Hospital Opens: The Arizona State Hospital, a psychiatric facility located in Phoenix, opened its doors on May 18, 1887. The hospital has a controversial history, including allegations of mistreatment of patients.

4. Gold Discovered in Bradshaw Mountains: On May 18, 1863, a group of prospectors discovered gold in the Bradshaw Mountains near Prescott, Arizona. This discovery led to a gold rush, with thousands of people flocking to the area in search of riches.

5. Sky Harbor Airport Dedicated: On May 18, 1952, Phoenix Sky Harbor International Airport was dedicated. Today, Sky Harbor is one of the busiest airports in the world, serving over 44 million passengers annually.