Where did the dollar sign ($) for U...

The American colonists used both the British pound and the Spanish dollar as monetary units. The Spanish dollar, or piece of eight, predominated, as it was the international standard during the 17th and 18th centuries. It also was the prototype for the 1785 American silver dollar. There are several theories about the origin of the dollar sign, but the Treasury Department believes that the Spanish P (for piastre, or piece of eight) gradually came to be overlaid with an S, resulting in a close equivalent of the dollar sign. The symbol was widely used before the adoption of the U.S. dollar.