What does the dollar sign($) represent?

The dollar sign is an abbreviation for "pesos." The Spanish dollar, also known as the "peso de 8 reales", was the principal coin in circulation in the U.S. up until 1794, when US began minting their own dollars. In handwriting, "pesos" was usually abbreviated lowercase "ps," with S above and to the right of the P and with the hook on the latter written with one or two deep strokes. As time went on, the P and the S tended to get mashed together and the result was $.

The dollar sign and the PS abbreviation were used interchangeably from around 1775 until the end of the century, after which the latter faded from view.