A score of things that made today's Phoenix:
1. ASU: In 1920, Tempe Normal School was awarding teaching certificates and providing high-school courses. From there it became Tempe State Teachers College (1925), Arizona State Teachers College (1929), Arizona State College (1945), and finally a university (1958). Today, under the dynamic leadership of Michael Crow, ASU is one of the largest universities in the United States. Among its five campuses/centers is the transformative downtown Phoenix location. The downside: Phoenix is by far the largest metropolitan areas in America with only one real, full-sized university.
2. Agriculture: A century ago, Phoenix was the center of a major agricultural empire thanks to its location in one of the planet's great alluvial river valleys. Anything would grow — just add water, which was abundant thanks to Theodore Roosevelt Dam and its successors. It's almost all gone. At one time, we could feed ourselves and exported produce and beef to the nation. Now Phoenix is almost entirely reliant on the 10,000-mile supply chain. A more foresighted place would have established agricultural trusts to preserve the citrus groves and Japanese flower gardens.
3. Air conditioning: Refrigerated air showed up in movie theaters and new hotels a century ago. Swamp coolers and central air units made Phoenix bearable for more people year-round (no more sleeping porches and wrapping oneself in wet sheets in summer). For awhile after World War II, Phoenix was also a center of air-conditioning manufacturing.