Peoria (/piˈɔːriə/) is a city in Maricopa and Yavapai counties in the U.S. state of Arizona. Located primarily in Maricopa County, it is a major suburb of Phoenix. According to 2010 Census Bureau releases, the population of the city is 154,065. Peoria is currently the sixth largest city in Arizona for land area, and the ninth largest for population. It was named after Peoria, Illinois. (The word peoria is a corruption of the Illini word for “prairie fire”.) Peoria is now larger in population than its namesake. It is the spring training home of the San Diego Padres and Seattle Mariners who share the Peoria Sports Complex. In July 2008, Money magazine listed Peoria in its "Top 100 Places to Live".

Peoria sits on flat gently sloping desert terrain in the Salt River Valley, and extends into the foothills of the mountains to the north. Seasonal rainfall and runoff from mountain snowmelt filled the Salt River, at times flooding the valley and wiping out months of backbreaking labor. If the area was to become habitable and productive all year, the cycle of flood and drought had to be replaced with a reliable supply of water that could be controlled year-round. The pioneers turned to irrigation. In 1868 John W. “Jack” Swilling organized a group of men to dig the first modern irrigation ditch in the Salt River Valley. Their success enticed more people to settle in the area and reap the benefits of a revitalized irrigation system.

Arizona (ⁱ/ɛrɪˈzoʊnə/; /ærɪˈzoʊnə/) (Navajo: Hoozdo Hahoodzo; O'odham: Alĭ ṣonak) is a state of the United States, located in the southwestern region of the country. Arizona is also part of the Western United States and of the Mountain West states. Arizona is the sixth most extensive and the 16th most populous of the 50 states. Its capital and largest city is Phoenix. The second largest city is Tucson, followed in population by eight cities of the Phoenix metropolitan area: Mesa, Chandler, Glendale, Scottsdale, Gilbert, Tempe, Peoria, and Surprise.

Arizona is the 48th state and last of the contiguous states to be admitted to the Union, and it achieved statehood on February 14, 1912. Arizona is noted for its desert climate in its southern half, where there are very hot summers and quite mild winters. The northern half of Arizona also features forests of pine, Douglas fir, and spruce trees, a very large, high plateau (the Colorado Plateau) and some mountain ranges—such as the San Francisco Mountains—as well as large, deep canyons, where there is much more moderate weather for three seasons of the year, plus significant snowfalls. There are ski resorts in the areas of Flagstaff and Alpine.