1856: Sonora Exploring and Mining Company is organized in Cincinnati to develop silver mines in southern Arizona. The Heintzelman Mine, near Arivaca, was the company's first development.

1997: Tucson becomes the first city in Arizona with an independent auditor to review citizen complaints against the Police Department.

2001: Randy Johnson, pitching in a spring training game for the Arizona Diamondbacks at Tucson Electric Park, hits and kills a dove with a 95-mph pitch.

Want to share an important event from Tucson's history? Email it to krumore@azstarnet.com.