In the 17th Century, this marked the edge of the city of New Amsterdam, and it was the location of the city's 12-foor palisade wall. The wall itself was torn down by the British in 1699 but the name "Wall Street" stuck.
By the late 18th century this was already becoming a financial centre - traders met at the Merchant Coffee House at the corner of Water Street, and under a buttonwood free outside to trade securities. (This buttonwood free is the site of the Buttonwood Agreement, which was the beginning of the New York Stock Exchange.)
The street is only 8 blocks long - as long today as you see it here in the late 1700s. If that seems extremely small remember: the skyscrapers are tall, rather than wide. Otherwise they'd be called Floorhuggers.