Arizona (; 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.
Arizona is one of the Four Corners states. Arizona has borders with New Mexico, Utah, Nevada, California, and Mexico, and it has one point in common with the southwestern corner of Colorado. Arizona has a -long international border with the Mexican states of Sonora and Baja California.
Arizona is the most populous landlocked state of the United States, ranking slightly ahead of Tennessee as of 2011. In addition to the Grand Canyon National Park, several national forests, national parks, and national monuments are located in Arizona. About one-quarter of Arizona is federal land that serves as the home of the Navajo Nation; the Hopi tribe; the Tohono O'odham; the Apache tribe; the Yaqui peoples; and various Yuman tribes, such as the Yavapai people, the Quechan people, and the Hualapai people.