1. On April 12, 1861, Confederate troops fired on Fort Sumter in South Carolina, marking the beginning of the American Civil War. Although Arizona did not become a state until 1912, many Arizona residents fought for both the Union and Confederate armies during the war.

2. On April 12, 1912, Arizona was admitted to the Union as the 48th state. The state had been a territory since 1863, and its admission was the culmination of a decades-long struggle for statehood.

3. In 1937, the Navajo Tribal Council was established, giving the Navajo Nation a formal government structure for the first time. Today, the Navajo Nation is the largest Native American tribe in the United States, spanning parts of Arizona, New Mexico, and Utah.

4. On April 12, 1945, Arizona senator and former presidential candidate Barry Goldwater joined the U.S. Army Air Corps. Goldwater would go on to serve in World War II and earn the rank of major before returning to Arizona and eventually entering politics.

5. On April 12, 1981, the first space shuttle mission was launched from Kennedy Space Center in Florida. Although the launch took place outside of Arizona, the state has played an important role in space exploration through organizations like the University of Arizona's Lunar and Planetary Laboratory and the Mars Exploration Program.