[bzbarsky]

The English East India Company was set up along lines pretty similar to today's corporations, and that happened almost 200 years before the constitution was written (1600, to be precise). By 1720 you definitely have bubbles involving corporate stocks (see South Sea Bubble).

By the time you get to the late 18th century (i.e. about when the Constitution was written) you have publications with titles like "A Treatise on the Law of Corporations"; just keep reading the Wikipedia entry above. That was published 7 years after the US Constitution was ratified, but of course the laws and corporations it was talking abot had been around for _quite_ a while at that point.