Phoenix, Arizona is a U.S. state.
The Arizona State Legislature is the state legislature of the U.S. state of Arizona . Interstate 40 ( I-40 ) is an east -- west Interstate Highway that has a 359.6 mi section in the U.S. state of Arizona connecting sections in California to New Mexico . 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 . A U.S. state is a constituent political entity of the United States of America .