Roosevelt, built just before statehood, was the first of a series of dams that produced a boom in agriculture by delivering reliable, year-round water supplies.
The evaporative cooler
Until the Arizona Cooler was introduced in the 1930s, everyone who could afford to leave the state in the summer did.
When Del Webb opened America's first true retirement community west of Phoenix on New Year's Day 1960, he hoped 10,000 people would show up, but 100,000 visited on that opening weekend.
The U.S. military
An estimated 17,000 pilots and more than 200,000 ground troops trained in Arizona during World War II, and afterward many moved here permanently.
A little magazine started in 1925 by state highway department engineers turned into the greatest vehicle for tourism promotion the state has ever seen.
- Selected by Bobbie Jo Buel