There are 4 US Post Offices in Greenlee County serving a total of 8,446 residents equating to 2,112 residents per post office. It's estimated that approximately 13,481 packages are handled across the 4 county post offices annually. Greenlee County is a county located in the southeastern part of the U.S. state of Arizona. As of the 2010 census its population was 8,437, making it the least populous county in Arizona. The county seat is Clifton. The economy of Greenlee County is dominated by the Morenci Mine, the largest copper mining operation in North America, and one of the largest copper mines in the world. As of 2008, the mine complex, owned by Freeport-McMoRan, had about 4,000 employees."