Little is known of the earliest indigenous cultures in Arizona, but they probably lived in the region as early as 25,000 B.C. A later culture, the Hohokam (A.D. 500–1450), were pit dwellers who constructed extensive irrigation systems. The Pueblo flourished in Arizona between the 11th and 14th cent. and built many of the elaborate cliff dwellings that still stand. The Apache and Navajo came to the area in c.1300 from Canada.
Probably the first Spanish explorer to enter Arizona (c.1536) was Cabeza de Vaca. Franciscan friar Marcos de Niza reached the state in 1539; he was followed by Francisco Vásquez de Coronado, who led an expedition from Mexico in 1540 in search of the seven legendary cities of gold, reaching as far as the Grand Canyon. Despite extensive exploration, the region was neglected by the Spanish in favor of the more fruitful area of New Mexico. Father Eusebio Kino, a Jesuit, founded the missions of Guevavi (1692) and Tumacacori (1696), near Nogales, and San Xavier del Bac (1700), near Tucson. The Spanish Empire, however, expelled the Jesuits in 1767, and those in Arizona subsequently lost their control over the indigenous people.
The Arizona region came under Mexican control following the Mexican war of independence from Spain (1810–21). In the early 1800s, U.S. mountain men, trappers and traders such as Kit Carson, trapped beaver in the area, but otherwise there were few settlers.
In the Treaty of Guadalupe Hidalgo (1848), ending the Mexican War (1846–48), Mexico relinquished control of the area N of the Gila River to the United States. This area became part of the U.S. Territory of New Mexico in 1850. The United States, wishing to build a railroad through the area S of the Gila River, bought the area between the river and the S boundary of Arizona from Mexico in the Gadsden Purchase (1853).
Arizona's minerals, valued even by prehistoric miners, attracted most of the early explorers, and although the area remained a relatively obscure section of the Territory of New Mexico, mining continued sporadically. Small numbers of prospectors, crossing Arizona to join the California gold rush (1849), found gold, silver, and a neglected metal—copper.
In 1861, at the outbreak of the Civil War, conventions held at Tucson and Mesilla declared the area part of the Confederacy. In the only engagement fought in the Arizona area, a small group of Confederate pickets held off Union cavalry NW of Tucson in the skirmish known as the battle of Picacho Pass.
In 1863, Arizona was organized as a separate territory, with its first, temporary capital at Fort Whipple. Prescott became the capital in 1865. Charles D. Poston, who had worked to achieve Arizona's new status, was elected as the territory's first delegate to the U.S. Congress. The capital was moved to Tucson in 1867, back to Prescott in 1877, and finally to Phoenix in 1889.
The region had been held precariously by U.S. soldiers during the intermittent warfare (1861–86) with the Apaches, who were led by Cochise and later Geronimo. General George Crook waged a successful campaign against the Apaches in 1882–85, and in 1886 Geronimo finally surrendered to federal troops. When Confederate troops were routed and Union soldiers went east to fight in the Civil War, settlement was abandoned. It was resumed after the war and encouraged by the Homestead Act (1862), the Desert Land Act (1877), and the Carey Land Act (1894)—all of which turned land over to settlers and required them to develop it.
In the 1870s mining flourished, and by the following decade the Copper Queen Company at Bisbee was exploiting one of the area's largest copper deposits. In 1877 silver was discovered at Tombstone, setting off a boom that drew throngs of prospectors to Arizona but lasted less than 10 years. Tombstone also became famous for its lawlessness; Wyatt Earp and his brothers gained their reputations during the famous gunfight (1881) at the O. K. Corral. By 1880 the Santa Fe and Southern Pacific railroads both extended into Arizona. Ranching began to thrive and sheep raising grew from solely a Navajo occupation to a major enterprise among white settlers. After 1897, the U.S. Forestry Bureau issued grazing permits to protect public land from depletion.
In 1912, Arizona, still a frontier territory, attained statehood. Its constitution created a storm, with such "radical" political features as initiative, referendum, and judicial recall. Only after recall had been deleted did President Taft sign the statehood bill. Once admitted to the Union, Arizona restored the recall provision.
Irrigation, spurred by the Desert Land Act and by Mormon immigration, promoted farming in the southern part of the territory. By 1900, diverted streams were irrigating 200,000 acres (80,940 hectares). With the opening of the Roosevelt Dam (1911), a federally financed project, massive irrigation projects transformed Arizona's valleys. Although Arizona's mines were not unionized until the mid-1930s, strikes occurred at the copper mines of Clifton and Morenci in 1915 and at the Bisbee mines in 1917.
During World War II, defense industries were established in Arizona. Manufacturing, notably electronic industries, continued to develop after the war, especially around Phoenix and Tucson; in the 1960s, manufacturing achieved economic supremacy over mining and agriculture in Arizona. During the 1970s and 80s the state experienced phenomenal economic growth as it and other Sun Belt states attracted high-technology industries with enormous growth potential.
Arizona has contributed several major figures to national politics. Among them, Senator Barry M. Goldwater, the unsuccessful 1964 Republican candidate for the U.S. presidency, was long the standard bearer for American conservatism. Democrat Stewart L. Udall served as secretary of the interior under presidents Kennedy and Johnson.
With the development of irrigation and hydroelectric projects along the Colorado River and its tributaries, water rights became a subject of litigation between Arizona and California. In 1963 the U.S. Supreme Court ruled that Arizona had rights to a share of the water from the Colorado's main stream and sole water rights over tributaries within Arizona. In 1968, Congress authorized the Central Arizona Project, a 335-mi (539-km) canal system to divert water from the Colorado River to the booming metropolitan areas of Phoenix and Tucson. The canal, which uses dams, tunnels, and pumps to raise the water 1,247 ft (380 m) to the desert plain, was opposed by environmentalists, who feared it would damage desert ecosystems. Construction was completed in 1991, at a cost of over $3.5 billion.
In 1992 a six-year political controversy ended when Arizona voters approved a proposal to observe an annual state holiday honoring Martin Luther King, Jr. The state again became a focus of national (and international) controversy in 2010 when it enacted a law requiring local law officers to check the status of someone stopped for an offense if the person is believed to an illegal alien; although that aspect of the law was upheld in 2012 by the U.S. Supreme Court, other aspects were struck down.