Tucson is a city in and the county seat of Pima County, Arizona, United States, and is home to the University of Arizona. It is the second largest city in Arizona behind Phoenix, with a population of 542,629 in the 2020 United States census, while the population of the entire Tucson metropolitan statistical area (MSA) is 1,043,433. The Tucson MSA forms part of the larger Tucson-Nogales combined statistical area (CSA). Both Tucson and Phoenix anchor the Arizona Sun Corridor. The city is 108 miles (174 km) southeast of Phoenix and 60 mi (97 km) north of the U.S.–Mexico border. Tucson is the 34th largest city and the 53rd largest metropolitan area in the United States (2014). 4K Resolution.