Date: Signed 1792
The Buttonwood Agreement is the precursor to the New York Stock Exchange. It was signed in 1792 under a Buttonwood tree on Wall St. - hence the name. Lucky it wasn't a Monkey Puzzle Tree - that would not be a dignified name at all.
The agreement itself is fairly simple - 24 local merchants agreed that they would trade only with one another, and that they would take a 0.25% commission on whatever they traded.
And in case you're thinking 1792 is too early for there to be stocks to trade, it wasn't - the first war bonds were released by Alexander Hamilton, in 1790, two years before, so you're wrong, and should probably keep your opinion to yourself.