How did the dollar get its sign?

The symbol $ written before the numerical amount is used for the US dollar and many other currencies. The sign’s actual origins are not certain, though it is possible it comes from the Pillars of Hercules, which flank the Spanish coat of arms on the Spanish dollars that were minted in the New World Mints. The Pillars of Hercules are in the form of two vertical bars and a swinging cloth band in the shape of an ‘S’. Another explanation is that the symbol for peso was the result of the abbreviation ‘ps’ – the p and s came to be written over each other, appearing like ‘$’. Another possibility is that the dollar sign is 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 in use before the formation of the United States.