Who came up with the $ sign and how?

Answer 1

The sign is attested in business correspondence between British North America and Mexico in the 1770s as referring to the Spanish-Mexican peso. The piastre was known as "Spanish dollar" in British North America, and in 1785, it was adopted as U.S. currency, together with both the term "dollar" and the $ sign.

The sign's ultimate origins are not certain. The most widely accepted explanation, according to the U.S. Bureau of Engraving and Printing here, is that "$" is a corruption of the letters "PS" or "PS" (for 'peso', as each letter could represent each syllable of "Pe-So") written over each other in Spanish. Eventually, the 'P' was reduced to a vertical line.

Another possibility is that it derives from the British notation 8/ for eight shilling, referring to the Spanish 8 reales coin ("piece of eight"), which later became the USA dollar. Others derive it from the Portuguese Cifrão sign . In Spain it is said that the sign of the old spanish peso "$" is the left Hercule's Column with the emblem of "Plus Ultra" that appears in the kingdom's Scutcheon of the Spanish Flag (see below).

Answer 2

The Dollar as the name of a currency existed long before USA was even formed!
It was used even in Shakespearean times---1554, etc-- in many European countries like Denmark, Sweden, Norway, Chezck, etc, and was called 'Thaler' [Greek 'Thalos'] and Dallar, from the mints in Europe from where the silver coins were mined and minted. It was adopted by the USA ,(When USA was formed on 4th July 1776 ) instead of the British Pound, as a currency for the whole of USA.
If you know your US history, the 'predominantly British ' colonies who came originally from Britain rebelled against the British King, and decided to form their own United States in America. It is nothing but the capital letters U and S, written one on top of the other, where the lower curve was dropped with frequent and hurried use!

Answer 3

http://en.wikipedia.org/wiki/%24_sign