The United States dollar (sign: $; code: 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. It is divided into 100 cents (200 half-cents prior to 1857).
The U.S. dollar is the currency most used in international transactions. Several countries use it as their official currency, and in many others it is the de facto currency.
The first dollar coins issued by the United States Mint (founded 1792) were similar in size and composition to the Spanish dollar. The Spanish and U.S. silver dollars circulated side by side in the United States, and the Spanish dollar remained legal tender until 1857. The coinage of various English colonies also circulated. The lion dollar was popular in the Dutch New Netherland Colony (New York), but the lion dollar also circulated throughout the English colonies during the seventeenth and early eighteenth centuries. Examples circulating in the colonies were usually worn so that the design was not fully distinguishable, thus they were sometimes referred to as "dog dollars".