Tucson badgeTucson [4] (Spanish Tucson, English Tucson [ˈtuːsɒn]) is a large city in the state of Arizona, USA and the administrative center of Pima County. It is one of the fastest growing cities in the United States. The population of the city itself - 545 975 inhabitants (2018) [1] [2], it is the second largest city in the state of Arizona after the capital of the state - Phoenix.