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 Pillars of Hercules on the Spanish Coat of arms on the Spanish dollars that were minted in the New World mints in Mexico City, Potosí, Bolivia, and in Lima, Peru. These Pillars of Hercules on the silver Spanish dollar coins take the form of two vertical bars (||) and a swinging cloth band in the shape of an "S".
Another explanation is that this symbol for peso was the result of a late 18th-century evolution of the scribal abbreviation "ps." The p and the s eventually came to be written over each other giving rise to $.
A fictional possibility suggested is that the dollar sign is the capital letters U and S typed one on top of the other. This theory, popularized by novelist Ayn Rand in Atlas Shrugged, does not consider the fact that the symbol was already in use before the formation of the United States.