Area code and exchange code is assigned to every constituent of city in the United States. The area and exchange codes of the telephone can be used to find information about a region. Area code 925 and exchange code 273 is assigned to Livermore. The latitude and longitude corresponding to 37.68 and -121.79 can be used to find an area on the map. At&t - Local - Caoperates most of the land lines in United States.