1. On April 26, 1928, construction began on Hoover Dam, which spans the Colorado River between Arizona and Nevada. The dam was completed in 1935 and remains an iconic symbol of engineering and infrastructure in the region.

2. In 1986, a nuclear power plant in Chernobyl, Ukraine melted down, causing a massive environmental disaster. On April 26 of that year, the first traces of radioactive material from the disaster were detected in the Tucson area of Arizona.

3. In 1905, a large earthquake struck the area around Jerome, Arizona. The earthquake was estimated to be around a magnitude 6.0 and caused significant damage to the town and surrounding areas.

4. On April 26, 1866, the Arizona Territory was established by an act of Congress. The territory eventually became the 48th state in the US, admitted to the Union on February 14, 1912.

5. The Arizona Diamondbacks, a Major League Baseball team based in Phoenix, played their first game on April 26, 1998. The team won the National League Championship in 2001 and the World Series in 2001, their fourth season of existence.