Phoenix is the anchor of the Phoenix metropolitan area, also known as the Valley of the Sun, which in turn is a part of the Salt River Valley. The metropolitan area is the 12th largest by population in the United States, with approximately 4.73 million people as of 2017. In addition, Phoenix is the seat of Maricopa County, and at 517.9 square miles (1,341 km2), it is the largest city in the state, more than twice the size of Tucson and one of the largest cities in the United States.
Settled in 1867 as an agricultural community near the confluence of the Salt and Gila Rivers, Phoenix incorporated as a city in 1881. It became the capital of Arizona in 1889. Located in the northeastern reaches of the Sonoran Desert, Phoenix has a hot desert climate. Despite this, its canal system led to a thriving farming community, many of the original crops remaining important parts of the Phoenix economy for decades, such as alfalfa, cotton, citrus, and hay (which was important for the cattle industry). Cotton, cattle, citrus, climate, and copper were known locally as the "Five C's" of Phoenix's economy. These industries remained the driving forces of the city until after World War II, when high-tech companies began to move into the valley and air conditioning made Phoenix's hot summers more bearable.
The city averaged a four percent annual population growth rate over a 40-year period from the mid-1960s to the mid-2000s. This growth rate slowed during the Great Recession of 2007–09, and has rebounded slowly. Phoenix is the cultural center of the Valley of the Sun, as well as the entire state.
For more than 2,000 years, the Hohokam people occupied the land that would become Phoenix. The Hohokam created roughly 135 miles (217 km) of irrigation canals, making the desert land arable. Paths of these canals would later become used for the modern Arizona Canal, Central Arizona Project Canal, and the Hayden-Rhodes Aqueduct. The Hohokam also carried out extensive trade with the nearby Anasazi, Mogollon and Sinagua, as well as with the more distant Mesoamerican civilizations. It is believed that between AD 1300 and AD 1450, periods of drought and severe floods led to the Hohokam civilization's abandonment of the area.
After the departure of the Hohokam, groups of Akimel O'odham (commonly known as Pima), Tohono O'odham and Maricopa tribes began to use the area, as well as segments of the Yavapai and Apache. The O'odham were offshoots of the Sobaipuri tribe, who in turn were thought to be the descendants of the formerly urbanized Hohokam.