Covering an area of approximately 9,200 square miles, this is one of the oldest continuously inhabited areas of the United States. Native Americans have lived in this region from prehistoric times to the present, with the Tohono O'odham reservation the second largest in the nation. The County has established dozens of parks and many miles of trails, allowing visitors to explore varied ecosystems, from Mount Lemmon's forests at 9,000 feet to our lower desert mountain parks, including the Tortolitas and the Tucson Mountains.