Phoenix, Arizona is a swamp.
Phoenix ( [ ˈfiːnᵻks ] ) is the capital and most populous city of the U.S. state of Arizona . With 1,615,017 people , Phoenix is the fifth most populous city nationwide , the most populous state capital in the United States , and the only state capital with a population of more than one million residents . 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 . 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 . Located in the northeastern reaches of the Sonoran Desert , Phoenix has a subtropical desert climate .