Area codes 864 and 821 are telephone overlay area codes in the North American Numbering Plan (NANP) for the western third of the U.S. state of South Carolina. The numbering plan area (NPA) comprises the areas of Greenville, Spartanburg, Anderson, and twelve surrounding counties. Other cities in the numbering plan area include Clemson, Gaffney, Greer, and Mauldin. It is largely coextensive with the Upstate region.