The United States dollar, or American dollar, adopted by the United States Congress in 1785, is the official currency of the United States. It is also widely used as a reserve currency outside the United States. Currently, the issuance of currency is controlled by the Federal Reserve Banking system.
The United States dollar uses the decimal system, consisting of 100 cents (symbol). In another division, there are 1,000 mills or ten dimes to a dollar; additionally, the term eagle was used in naming gold coins. However, only cents are in everyday use as divisions of the dollar; "dime" is used solely as the name of the coin with the value of 10?, while "eagle" and "mill" are largely unknown to the general public, though mills are sometimes used in matters of tax levies and gasoline prices.
A few nations besides the United States use the United States dollar as their official currency, a process known as official dollarization. Ecuador, El Salvador, and East Timor all adopted the currency independently. The former members of the US-administered Trust Territory of the Pacific Islands, which included Palau, the Federated States of Micronesia, and the Marshall Islands, chose not to issue their own currency after becoming independent.
At the present time, the United States dollar remains the world's foremost reserve currency, primarily held in $100 denominations. The majority of U.S. notes are actually held outside the United States. Economist Paul Samuelson and others maintain that the overseas demand for dollars allows the United States to maintain persistent trade deficits without causing the value of the currency to depreciate and the flow of trade to readjust.
United States dollar coins have found little popular acceptance in modern circulation in the United States, despite several attempts since 1971 to phase-in a coin in place of the one-dollar bill. This contrasts with many other currencies, where the one-unit denomination is only in coin, such as the Canadian Loonie, British Pound sterling, Australian Dollar (both $1 and $2) and Euro coin. The failure to simultaneously withdraw the dollar bill and weak publicity efforts have been cited by coin proponents as primary reasons for the failure of the dollar coin to gain popular support.
There was a process to unify the design of all the currency. The variety of large note design gave way to common elements and a common look for the small notes. This changed little over the years, until a radically redesigned $100 bill was introduced in the 1990's, inaugurating a gradual change in all the currency for security reasons. United States currency had never featured anti-counterfeiting devices like watermarked paper and security threads, which had appeared in foreign money decades earlier.
All the small notes featured a portrait of Washington for the $1 note, Jefferson for $2, Lincoln for $5, Hamilton for $10, Jackson for $20, Grant for $50, Franklin for $100, McKinley for $500, Cleveland for $1000, Madison for $5000, and Chase for the $10,000. When one series of $100,000 notes was issued (1934 Gold Certificates), Wilson was put on them. Although these portraits are often called "dead presidents," three of them, Hamilton, Franklin, and Chase, were never Presidents. Large notes had featured many more portraits, including Martha Washington, William Tecumseh Sherman, John Marshall, James Monroe, the Sioux Indian Takokainyanka, Samuel F.B. Morse, and many others.