They were aware of corporations as a business structure. English public stock corporations had played a major role in the founding of the colonies of Virginia (Virginia Company of London and Virginia Company of Plymouth) and Massachusetts (Massachusetts Bay Company), and also in the history of Canada (Hudson's Bay Company). They were certainly aware of these concepts. Corporations are older than the United States is.
That said, it was a much rarer business structure, only used for very large firms, because incorporating a company required a special act of Parliament – a power inherited by the colonial (and thereafter state) legislatures. It was not until the 19th century that it became the norm to for companies to be incorporated under a general incorporation statute, as opposed to a separate incorporation statute being passed to incorporate each individual company.
Business activity was vastly different at the founding