United States Dollar

The dollar (USD) is the unit of currency of the United States. The U.S. dollar has also been adopted as the official and legal currency by the governments in a few other countries. 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. It is divided into 100 cents.

Background
Taken over by the Congress of the Confederation of the United States on July 6, 1785, the U.S. dollar is the currency most used in international transactions. Several countries use the U.S. dollar as their official currency, and many others allow it to be used in a de facto capacity. In 1995, over US $380 billion were in circulation, two-thirds of which was outside the United States. By 2005, that figure had doubled to nearly $760 billion, with an estimated half to two-thirds being held overseas, representing an annual growth rate of about 7.6%. However, as of December 2006, the dollar was surpassed by the euro in terms of combined value of cash in circulation. Since then the current value of euro cash in circulation has risen to more than €695 billion, equivalent to US$1.029 trillion at current exchange rates.

Overview
The U.S. dollar uses the decimal system, consisting of 100 equal cents (symbol ¢). In another division, there are 1,000 mills or ten dimes to a dollar; additionally, the term eagle was used in the Coinage Act of 1792 for the denomination of ten dollars, and subsequently was used in naming  gold coins. In the second half of the 19th century there were occasional discussions of creating a $50 gold coin, which was referred to as a "Half Union," thus implying a denomination of 1 Union = $100. 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. When currently issued in circulating form, denominations equal to or less than a dollar are emitted as U.S. coins while denominations equal to or greater than a dollar are emitted as Federal Reserve notes (with the exception of gold, silver and platinum coins valued up to $100 as legal tender, but worth far more as bullion). (Both one-dollar coins and notes are produced today, although the note form is significantly more common.) In the past, paper money was occasionally issued in denominations less than a dollar (fractional currency) and gold coins were issued for circulation up to the value of $20 (known as the "double eagle", discontinued in the 1930s).

U.S. coins are produced by the United States Mint. U.S. dollar banknotes are printed by the Bureau of Engraving and Printing, and, since 1914, have been issued by the  Federal Reserve. The "large-sized notes" issued before 1928 measured 7.42 inches (188mm) by 3.125 inches (79.4mm); small-sized notes, introduced that year, measure 6.14 inches (156mm) by 2.61 inches (66 mm) by 0.0043 inches (0.11 mm).