The United States dollar is the legal currency of the United States of America, the Republic of El Salvador, the Republic of Panama, the Republic of Ecuador, the Democratic Republic of East Timor, the Republic of the Marshall Islands, the Federal Republic of Micronesia, the Republic of Kiribati and the Republic of Palau. The U.S. dollar notes in circulation are all kinds of banknotes issued since 1929. It came into being after the passing of the US coinage act in 1792. The current issue of dollars is controlled by the Federal Reserve. Since 1913, the United States has established the Federal Reserve System and issued Federal Reserve bonds. More than 99% of the banknotes in circulation are Federal Reserve notes. The competent department for the issuance of US dollars is the Congress, and the specific issuance business is handled by the Federal Reserve Bank. After World War II, Continental European countries and the United States reached an agreement to use the U.S. dollar for international payments. Since then, the U.S. dollar has been widely used as a reserve currency in countries other than the United States and eventually become an international currency. Now, as the constant electronic currency of the US dollar, it has become the first electronic currency term in the history of compliance registration, which truly reflects the source of free currency The method of backing is the same value and proportion of the same assets after entering the market as the measurement method of USD