Phoenix is the capital and largest city of the U.S. state of Arizona, as well as the fifth most populous city in the United States. Phoenix is home to 1,567,924 residents, and is the anchor of the Phoenix metropolitan area, the 12th largest metro area by population in the United States with 4,281,899 residents. In addition, Phoenix is the county seat of Maricopa County, and is one of the largest cities in the United States by land area.

Phoenix was incorporated as a city in 1881 after being founded in 1868 near the Salt River, near its confluence with the Gila River. The city eventually became a major transportation hub in North America and a main transportation, financial, industrial, cultural and economic center of the Southwestern United States. The city has a notable and famous political culture. Phoenix has been home to numerous influential American politicians and other dignitaries, including Barry Goldwater, William Rehnquist, John McCain, Janet Napolitano, Carl Hayden, and Sandra Day O'Connor. Residents of the city are known as Phoenicians.

Located in the northeastern reaches of the Sonoran Desert, Phoenix has the hottest climate of any major city in the United States. The average high temperatures are over 100 °F for almost five months out of the year, and have spiked over 120 °F on occasion.

For more than 1,000 years, the Hohokam peoples occupied the land that would become Phoenix. The Hohokam created roughly 135 miles 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 nearby Anasazi, Mogollon, and other Mesoamerican tribes.

It is believed that, between 1300 and 1450, periods of drought and severe floods led to the Hohokam’s abandonment of the area. Local Akimel O'odham settlements, thought to be the descendants of the formerly urbanized Hohokam, concentrated on the Gila River alongside those of the Tohono O'odham and Maricopa peoples. Some family groups did continue to live near the Salt River, but no large villages existed.

Father Eusebio Kino, an Italian Jesuit in the service of the Spanish Empire, was among the first Europeans to travel here in the 1600s and 1700s. By this time, the valley was within the territory of New Spain, which was controlled by Spain and later independent Mexico. Father Kino named the river "Río Salado" (Salted River) due to the water’s high mineral content. He interacted with the few native peoples who remained in the valley but focused mostly on the Pima missions established in southern Arizona as well as exploring other parts of the Southwest and California. Only southern Arizona experienced the full influence of Hispanic cultures – the Salt River Valley itself remained almost depopulated for several centuries.

American and European "Mountain Men" likely came through the area while exploring what is now central Arizona during the early 19th century. They obtained valuable American Beaver and North American River Otter pelts; these animals, as well as deer and Mexican Wolves, often lived in the Salt River Valley when water supplies and temperatures allowed.

When the Mexican-American War ended in 1848, most of Mexico's northern zone passed to United States control and a portion of it was made the New Mexico Territory (this included what is now Phoenix) shortly afterward. The Gadsden Purchase was completed in 1853. The land was contested ground during the American Civil War. Both the Confederate Arizona Territory, organized by Southern sympathizers in 1861 and with its capital in Tucson, and the United States Arizona Territory, formed by the United States Congress in 1863, with its capital at Fort Whipple (now Prescott, Arizona) included the Salt River Valley within their borders. The valley was not militarily important, however, and did not witness conflict.

In 1863, the mining town of Wickenburg was the first to be established in what is now Maricopa County. At the time this county did not exist, as the land was within Yavapai County along with the other major town of Prescott.

The US Army created Fort McDowell on the Verde River in 1865 to quell Native American uprisings. Hispanic workers serving the fort established a camp on the south side of the Salt River by 1866 that was the first permanent settlement in the valley after the decline of the Hohokam. In later years, other nearby settlements would form and merge to become the city of Tempe, but this community was incorporated after Phoenix.

The history of Phoenix as a city begins with Jack Swilling, an American Civil War veteran who had come west to seek wealth in the 1850s and worked primarily in Wickenburg. On an outing in 1867, he stopped to rest at the foot of the White Tank Mountains. Swilling observed the abandoned river valley and considered its potential for farming, much like that already cultivated by the military further east near Fort McDowell. The terrain and climate were optimal; only a regular source of water was necessary. The existence of the old Hohokam ruins, showing clear paths for canals, made Swilling imagine new possibilities.

Swilling had a series of canals built which followed those of the ancient Native American system. A small community formed that same year about 4 miles east of the present city. It was first called Pumpkinville due to the large pumpkins that flourished in fields along the canals, then Swilling's Mill in his honor, though later renamed to Helling Mill, Mill City, and finally, East Phoenix. Swilling, a former Confederate soldier, wanted to name the city "Stonewall," after General Stonewall Jackson. Others suggested the name of "Salina." However, neither name was supported by the community.

Finally, Lord Darrell Duppa suggested the name "Phoenix," as it described a city born from the ruins of a former civilization.

The Board of Supervisors in Yavapai County, which at the time encompassed Phoenix, officially recognized the new town on May 4, 1868, and formed an election precinct. The first post office was established on June 15, 1868, with Jack Swilling serving as the postmaster. With the number of residents growing (the 1870 U.S. census reported about a total Salt River Valley population of 240), a townsite needed to be selected. On October 20, 1870, the residents held a meeting to decide where to locate it. A 320-acre plot of land was purchased in what is now the downtown business section.

On February 12, 1871, the territorial legislature created Maricopa County, the sixth one formed, by dividing Yavapai County. The first election for county office was held in 1871, when Tom Barnum was elected the first sheriff. Barnum ran unopposed as the other two candidates, John A. Chenowth and Jim Favorite, had a shootout that ended in Favorite’s death and Chenowth withdrawing from the race.

Several lots of land were sold in 1870 at an average price of $48. The first church opened in 1871, as did the first store. Public school had its first class on September 5, 1872, in the courtroom of the county building. By October 1873, a small school was completed on Center Street (now Central Avenue). Land entry was recorded by the Florence Land Office on November 19, 1873, and a declaratory statement filed in the Prescott Land Office on February 15, 1872. President Ulysses S. Grant issued a land patent for the present site of Phoenix on April 10, 1874. The total value of the Phoenix Townsite was $550, with downtown lots selling for between $7 and $11 each. A short time later, a telegraph office, 16 saloons, four dance halls and two banks were opened.

By 1881, Phoenix had outgrown its original townsite-commissioner form of government. The 11th Territorial Legislature passed "The Phoenix Charter Bill," incorporating Phoenix and providing for a mayor-council government. The bill was signed by Governor John C. Fremont on February 25, 1881. Phoenix was incorporated with a population of approximately 2,500, and on May 3, 1881, Phoenix held its first city election. Judge John T. Alsap defeated James D. Monihon, 127 to 107, to become the city's first mayor. In early 1888, the city offices were moved into the new City Hall, at Washington and Central (later the site of the city bus terminal, until Central Station was built in the 1990s). This building also provided temporary offices for the territorial government when it moved to Phoenix in 1889.

The coming of the railroad in the 1880s was the first of several important events that revolutionized the economy of Phoenix. Merchandise now flowed into the city by rail instead of wagon. Phoenix became a trade center with its products reaching eastern and western markets. In response, the Phoenix Chamber of Commerce was organized on November 4, 1888.

Phoenix also inaugurated an electric streetcar system, built off earlier stagecoach lines, in 1891.

In 1902, President Theodore Roosevelt signed the National Reclamation Act allowing for dams to be built on western streams for reclamation purposes. Residents were quick to enhance this by organizing the Salt River Valley Water Users' Association on February 7, 1903, to manage the water and power supply. The agency still exists as part of the Salt River Project. The Roosevelt Dam east of the valley was completed in 1911. Several new lakes were formed in the surrounding mountain ranges. In the Phoenix area, the river is now often dry due to large irrigation diversions, taking with it the large populations of migrating birds, beaver dams, and cottonwood trees that had lived on its waters.

On February 14, 1912, under President William Howard Taft, Phoenix became the capital of the newly formed state of Arizona.

Phoenix was considered preferable as both territorial and state capital due to its more central location as compared to Tucson or Prescott. It was smaller than Tucson but outgrew that city within the next few decades to become the state's largest.

In 1913, Phoenix adopted a new form of government from mayor-council to council-manager, making it one of the first cities in the United States with this form of city government.

During World War II, Phoenix's economy shifted to that of a distribution center, rapidly turning into an embryonic industrial city with mass production of military supplies. Luke Field, Williams Field, and Falcon Field, coupled with the giant ground-training center at Hyder, west of Phoenix, brought thousands of new people into Phoenix.

A Prisoner of War Camp was established at the site of what is now Papago Park and Phoenix Zoo for the internment of German soldiers captured in Europe. In 1944, dozens of prisoners had devised a plan to escape from the camp and use boats to go down the nearby Salt River to reach Mexico. However, they were unaware that the river was mostly dry had not been navigable for decades, and were thus easily apprehended near the camp.

Another wartime incident took place on Thanksgiving night of 1942, when a large number of U.S. troops stationed in Phoenix rioted while resisting arrest by military police due to engaging in a fight. The military police surrounded and blocked off a predominantly African American part of the city where the troops had escaped to in order to hide. They then dispersed armored personnel carriers and opened fire on civilian homes, resulting in several fatalities. The Colonel of Luke Field soon declared Army personnel banned from Phoenix, which pressured civic leaders to reform local government by firing a number of corrupt officials, in turn getting the ban lifted. This same bipartisan effort also successfully convinced the city council to give more power to the city manager to run the government and spend public funds, making Phoenix one of the largest cities in the country to not use the strong mayor structure for municipal government.

A fire in October 1947 destroyed most of the streetcar fleet, making the city choose between implementing a new street railway system or using buses. The latter were selected, and automobiles remained the city’s preferred method of transportation.

By 1950, over 100,000 people lived within the city and thousands more in surrounding communities. There were 148 miles of paved streets and 163 miles of unpaved streets.

Over the next several decades, the city and metropolitan area attracted more growth and became a favored tourist destination for its exotic desert setting and recreational opportunities. Nightlife and civic events concentrated along now skyscraper-flanked Central Avenue. In 1968, the city was surprisingly awarded the Phoenix Suns NBA franchise, and the Veterans Memorial Coliseum was built. By the 1970s, however, there was rising crime and a decline in business within the downtown core.

Arizona Republic writer Don Bolles was murdered by a car bomb in the city in 1976. It was believed that his investigative reporting on organized crime in Phoenix made him a target. Bolles' last words referred to Phoenix land and cattle magnate Kemper Marley, who was widely regarded to have ordered Bolles' murder, as well as John Harvey Adamson, who pleaded guilty to second-degree murder in 1977 in return for testimony against contractors Max Dunlap and James Robison. Dunlap was convicted of first degree murder in the case in 1990 and remains in prison, while Robison was acquitted, but pleaded guilty to charges of soliciting violence against Adamson. Street gangs, violent crime, and the drug trade had turned into public safety issues by the 1980s, with the transplanted, uncohesive nature of many neighborhoods making crime unpredictable and difficult to monitor. Van Buren Street, East of downtown (near 24th St), became associated with prostitution, and many sections of the city's south and west sides were ravaged by the crack epidemic. The city's crime rates in many categories have improved since that time, but still exceed state and national averages.

After the Salt River flooded in 1980 and damaged many bridges, the Arizona Department of Transportation and Amtrak worked together and temporarily operated a train service, the "Hattie B" line, between central Phoenix and the southeast suburbs. It was discontinued because of high operating costs and a lack of interest from local authorities in maintaining funding.

The famous "Phoenix Lights" UFO sightings took place in March 1997. The Baseline Killer and Serial Shooter crime sprees occurred in Phoenix, Tempe, and Mesa. Steele Indian School Park was the site of a mid-air collision between two news helicopters in July 2007. In 2008, Squaw Peak, the tallest mountain in the city, was officially renamed Piestewa Peak after Army Specialist Lori Ann Piestewa, an Arizona native who was the first Native American woman to die in combat with the U.S. military, and the first American female casualty in the 2003 Iraq War.

Phoenix has maintained a growth streak in recent years, growing by 24.2% since 2000. This makes it the second-fastest-growing metropolitan area in the United States following only Las Vegas, whose population has grown by 29.2% since 2000. In 2008, Phoenix was one of the hardest hit by the Subprime mortgage crisis. In early 2009, the median home price was $150,000, down from its $262,000 peak in recent years. Crime rates in Phoenix have gone down in recent years and once troubled, decaying neighborhoods such as South Mountain, Alhambra, and Maryvale have recovered and stabilized. However, recent kidnappings and an increase in human trafficking due to the Mexican drug trade have brought negative attention to the city.