The origin of the dollar sign is uncertain and has been explained in different ways. The most widely accepted explanation is that the symbol came up in the 1770s. It was first seen in the business documents of English-Americans who had business correspondences with Spanish-Americans. The libertarian philosopher and author Ayn Rand, in her 1957 novel, Atlas Shrugged had written a chapter on the dollar sign. She claimed that a dollar was a symbol of American currency and of the nation's economic freedom. According to her, the dollar sign with two slashes came from the letters U and S of the United States. A capital U superimposed over a capital S, minus the lower part of the U. There is no documentary evidence that supports this theory. It seems clear that the dollar sign was already in use by the time the United States was formed. This theory is also proven false in Cajori's book, A History of Mathematical Notations Vol. II published in 1929. ► The symbol became popular in the early 1800s when the first official U.S. dollars were being issued. Before this, the symbol was already in use as an abbreviation for the Spanish currency, peso. While financial documents regarding pesos were written, the abbreviation for peso was used. For example 1 peso to 1 p. The plural form, pesos, was written as pˢ. As it was required to write pˢ a number of times in financial documents, p was merged with the super scripted s as one. The top half of this symbol then developed something resembling a double vertical lined dollar sign. In due course of time, the English-American colonists started writing the p with just one downward stroke vertically slashing the s, forming the $. Around the same time when the U.S. was minting its first dollar coins, in the early 1800s, Spanish currency was circulated in the U.S. and around the world. As the Spanish currency became popular, the U.S. chose to duplicate the weight and material of the Spanish coins, and hence the value, to make the U.S. dollar coins. So, the same symbol was used to denote the U.S. dollar and the Spanish peso. ► It is widely believed that out of the four names for Spanish dollar, as the three names, i.e. pesos, piastres and pieces of eight start with p and pluralize with s, abbreviations such as p and ps came to be used. At times, ps was written as pˢ i.e. p with a superscript s. Gradually, the letters were joined together, the p was reduced to a single stroke, and the symbol $ was formed with double verticals and also with a single vertical stroke. ► The dollar sign being written sometimes with two vertical strokes can possibly be explained with another theory. This theory states that the peso coin had two pillars engraved on the reverse side to represent the Pillars of Hercules at Gibraltar with a banner curling between them, and the words, Plus Ultra on it. The words indicate that beyond the Pillars of Hercules there were other lands. That coin was called the Pillar Dollar in the British colonies in North America, and the two pillars have possibly become the two strokes in the dollar sign. ► It is also believed that the dollar sign may have come from a Roman coin called sestertius, which had the alphabets HS as its currency sign. When the letters were superimposed, it formed the dollar sign with two vertical strokes. ► Some believe that the dollar sign have originated from the German Thaler, a coin on which there was a crucified Christ on one side and a serpent hanging from a cross on the other. ► Another theory maintained that the dollar sign may have come from Hermes, the Greek god of bankers, thieves, and pranksters. One of his symbols was the caduceus, a rod from which ribbons or snakes dangled in a sinuous curve. Many also believe that the dollar sign is a version of the IHS, the Greek abbreviation of the name Jesus. The name dollar actually came from an ancient silver coin from Europe. This coin called Thaler, was used everywhere in Europe long ago, as early as the middle of 15th century. Thaler is a short form of the name Joachimsthaler, which came from its city of origin, Joachimsthal in Bohemia. The word Thal means valley. Therefore, thaler pertains to a thing that comes from valley. Gradually, the term, Thaler evolved into more versions like Tolar in Slovenia and Dollar in many countries. In some of the oldest documents having the dollar sign, both the double and single-slashed versions were mentioned in the same document, referring to the Spanish peso. Both these forms are original. The dollar symbol in those documents clearly reveal that the symbol is derived from the interchanging of p and s. Several other explanations have been proposed for how the dollar symbol came into existence. However, the PS theory is now accepted to a great degree.