As agreed upon by the International Telecommunication Union, the international country code for the United States is 1, with the same prefix used for Canada and a majority of the Caribbean. The dial out code for the United States is 011.
According to the International Telecommunication Union website, the organization, which was founded in 1865 and is headquartered in Geneva, Switzerland, is comprised of 193 member countries and over 700 private sector companies. The organization assigns international calling codes and dial out codes. The United States has been assigned a country code of 1 and a dial out code, also called an international call prefix, of 011. Most international calls to the United States require dialing 011 followed by 1 then the area code and number.