In 1913, the Federal Reserve System was created by Congress to issue money known as Federal Reserve Notes backed by a new central bank. This bank is a private bank with regional branches run by a board of governors with the chairman appointed by the President of the United States. It is not owned or part of the US government. The US treasury continued to issue US money in the form of gold and silver coins and gold and silver notes (paper money). Gold was recalled by President Roosevelt in 1934. Silver coins continued to be issued by the treasury until the silver in them became worth more than paper money and bank deposits in the 1960’s. Silver certificates were also issued by the treasury as paper money and for some time circulated along with Federal Reserve notes until the treasury stopped redeeming them for silver. Today these coins are in collectors hands. Circulated silver coins trade based on the price of silver as they are 90% silver.
In 1944 at the Bretton Woods conference, a new world monetary system was formed with the US dollar as the worlds reserve currency. Other currencies would trade at fixed rates to the US dollar. Central Banks could buy gold from the Federal Reserve at $35 per troy ounce. In 1974 President Nixon stopped the gold convertibility. All currencies would float as would gold. The US dollar would continue to be the worlds reserve currency.
Rumors are that the dollar will stop being the worlds reserve currency. This happened to the British Pound. The BP was worth 5.00 US dollars. Now it is $1.50.