1. Apache Chief Geronimo Surrenders (1886)
On August 18, 1886, Apache Chief Geronimo finally surrendered to General Nelson A. Miles near Skeleton Canyon in southeastern Arizona, marking the end of the Indian Wars in the region. Geronimo had been leading his small band of warriors on raids and skirmishes against white settlers and the U.S. Army for over a decade, and his surrender finally brought peace to the region.

2. Arizona Becomes a State (1911)
On August 18, 1911, Arizona officially became the 48th state in the Union. It had been a territory since 1863, and its path to statehood was long and contentious. The main issue was whether Arizona would allow recall elections, which were seen as a way for the public to hold elected officials accountable. Ultimately, the state was formed with recall elections enshrined in its constitution.

3. First Flight Across the Grand Canyon (1919)
On August 18, 1919, two army pilots named Lieutenants Davidson and Blanding made the first flight across the Grand Canyon, which was then still largely unexplored. They took off from a makeshift runway on the South Rim and landed on the North Rim two hours later, making history in the process.

4. Mo Udall Dies (1998)
On August 18, 1998, Mo Udall, a longtime congressman from Arizona, died at the age of 76. Udall had served in the House of Representatives for 30 years, during which time he became known for his wit, his integrity, and his willingness to work across the aisle to get things done. He was also instrumental in passing landmark environmental legislation, such as the Clean Air Act.

5. Arizona Diamondbacks Begin Play (1998)
On August 18, 1998, the Arizona Diamondbacks played their first game as a Major League Baseball team, hosting the Colorado Rockies at Bank One Ballpark (now Chase Field) in Phoenix. The Diamondbacks were one of two expansion teams added to the league that year, along with the Tampa Bay Devil Rays. They went on to finish their inaugural season with a 65-97 record.