The Salt River valley was occupied as early as 1300 AD by prehistoric Indians, now known as the Hohokam culture, who developed a system of irrigation canals before disappearing in the early 15th century. In 1867 Jack Swilling visited the area and, noticing the remnants of the ancient canals, organized an irrigation company; new canals were built, and a village was founded. An associate of Swilling, Darrel Duppa, was likewise impressed by evidences of the prehistoric culture, and predicted that, like the legendary phoenix which had been consumed by fire but arose from its own ashes, so would the Salt River city be born from the ancient Indian ruins. The settlement was thus named Phoenix and was incorporated in 1881. Phoenix became the seat of the territorial government in 1889 and remained the capital when Arizona attained statehood in 1912.

Phoenix developed as the commercial focus of the extensive Salt River irrigation projects, which are fed from the Roosevelt Dam on the Salt River 50 miles (80 km) northeast of the city. Diversified manufacturing, which was almost nonexistent before 1940, has now become the city's chief source of income. Among its manufactures are aircraft and electronic components, aluminum extrusions, agricultural chemicals, and air-conditioning equipment. The irrigated farmlands that surround the city produce lettuce and other vegetables, melons, citrus fruits, cotton, and olives. The economy is further augmented by mining, timbering, tourism, and military airfields and test stations.

Partly owing to its warm, extremely sunny climate, Phoenix was one of the fastest-growing cities of the United States in the decades after World War II; its population grew from about 100,000 in 1950 to more than 980,000 by 1990. The city also expanded greatly in area and now occupies 420 square miles (1,088 square km) of the Salt River valley. Among the city's notable buildings is the State Capitol, which was constructed of native tufa in Neoclassic style, with two additional wings for the House of Representatives and the Senate. The Phoenix Civic Plaza is a six-square-block convention center.