What is the historical origin of the dollar symbol ($)?

The Dollar sign first shows up in some very early American and Spanish business correspondence (around the 1770s). The exact reason why it is $ - is still a matter of much debate and controversy.

Three great articles to read on this are:

• The Dollar Mark and the Story of Its Origin - NYT Article - http://query.nytimes.com/mem/arc... (PDF)
• Where Do Currency Symbols Come From? - Slate Magazine: http://www.slate.com/articles/ne...
• Wikipedia - The Dollar Sign - http://en.wikipedia.org/wiki/Dol...