As of September 2014, the area code 976 was not assigned to a city or state. It is a designated area code for the United States.
There is a list of area codes that have been generated but have not yet been assigned. These are produced for future use, when a region becomes so populous that a new area code is necessary. A user can search up the city and state to which an area code is issued online using a variety of websites. AreaCode.org is one of these pages that is accurate and current as of 2014.