Ghostly cliff dwellings, such as Canyon de Chelly, contrast sharply with Phoenix and Tucson, where one out of three Arizonans live. The state's population has doubled in the past 20 years, and today smog often shrouds Phoenix, once favored by asthmatics for its clean, dry air. Service industries and high-tech and aerospace manufacturing have eclipsed the "three C's"—copper, cattle, and cotton; irrigated agribusiness remains important. The multibillion-dollar Central Arizona Project river diversion helps slake Arizona's thirst.