1. In 1868, the first known horse race was held in Arizona Territory on May 16th in Florence. Racing quickly became a popular pastime in the area.

2. On May 16, 1910, Arizona officially became a state. This day is celebrated annually as Arizona Statehood Day and is a state holiday.

3. In 1969, a groundbreaking ceremony was held for the Glen Canyon Dam on May 16th, which created Lake Powell and provided hydroelectric power to the region.

4. On May 16, 1985, the Navajo Nation Council voted to reject a proposed settlement in a longstanding water rights dispute with the state of Arizona.

5. In 2000, the Phoenix Suns defeated the Los Angeles Lakers in Game 1 of the Western Conference Finals on May 16th, marking the first time the Suns had advanced to the NBA Conference Finals since 1993.