Tucson, with a metro population of just over one million, is the state's second-largest city. Located in Pima County, approximately southeast of Phoenix, it was incorporated in 1877, making it the oldest incorporated city in Arizona. It is home to the University of Arizona. Major incorporated suburbs of Tucson include Oro Valley and Marana northwest of the city, Sahuarita south of the city, and South Tucson in an enclave south of downtown. It has an average July temperature of 100 °F (38 °C) and winter temperatures averaging 65 °F (18 °C). Saguaro National Park, just west of the city in the Tucson Mountains, is the site of the world's largest collection of Saguaro cacti.