The Tohono O'odham Nation is the collective government body of the Tohono O'odham tribe in the United States. The Tohono O’odham Nation governs four separate pieces of land for a combined area of making it the second largest Native American land holding in the United States. These lands are located within the Sonoran Desert of south central Arizona and are directly exposed to the Mexico–United States border for along its southern border. The Nation is organized into 12 local districts and employs a tripartite system of government. Sells, Arizona is the Nation's largest community and functions as its capital. The Nation has approximately 28,000 enrolled members, the majority of who live off the reservations.