The U.S. dollar is the currency most used in international transactions. Although U.S. dollar is a fiat currency, several countries use it as their official currency, and in many others it is the de facto currency.The United States dollar (sign: $| USD) is the unit of currency of the United States The U.S. dollar is normally abbreviated as the dollar sign, $, or as USD or US$ to distinguish it from other dollar-denominated currencies and from others that use the $ symbol.
The symbol $, usually written before the numerical amount, is used for the U.S. dollar (as well as for many other currencies). The sign's ultimate origins are not certain, though it is possible that it comes from the symbol for the New Spanish (Mexican) peso which in turn comes from the Spanish Coat of arms. This takes the form of two vertical bars and a swinging cloth band in the shape of an "S". An equally accepted, and better documented, explanation is that it is this symbol for peso was the result of a late eighteenth-century evolution of the scribal abbreviation "ps." The p and the s eventually came to be written over each other giving rise to $.
The United States dollar is unique in that there have been more than 10 types of banknotes, such as Federal Reserve Bank Note, gold certificate, and United States Note. The Federal Reserve Note is the only type that remains in circulation since the 1970s.
The largest denominations of currency currently printed or minted by the United States are the $100 bill and the $100 one troy ounce Platinum Eagle.
Currently printed denominations are $1, $2, $5, $10, $20, $50, and $100. Notes above the $100 denomination ceased being printed in 1946 and were officially withdrawn from circulation in 1969. These notes were used primarily in inter-bank transactions or by organized crime; it was the latter usage that prompted President Richard Nixon to issue an executive order in 1969 halting their use. With the advent of electronic banking, they became less necessary. Notes in denominations of $500, $1,000, $5,000, $10,000, and $100,000 were all produced at one time; see large denomination bills in U.S. currency for details.
