Corporations weren't citizens in 1776. It only took us 100 years or so to fuck that piece of it up. Nothing in the original Constitution or Declaration requires capitalism.
Arguably, corporations were more powerful then than they are now. Wars were fought because of the British East India Company - in 1778, it had a private army of 67,000 soldiers, over 50% more than the total strength of the American militia at that time.
The British East India Company didn't just have its own standing army. It also (since 1765) held the legal right to collect taxes in Bengal. For a large portion of India, it was the government.
Corporations aren't citizens now. If you mean "corporations weren't considered 'persons' in the scope of the 14th Amendment" in 1776 (or even, say, when the Constitution was first adopted), that's true, but then neither was anyone else.
Corporations, of course, have been legal persons in the general sense since the corporate form was invented; that's the whole point of the form.
http://www.ribbonfarm.com/2011/06/08/a-brief-history-of-the-...
Arguably, corporations were more powerful then than they are now. Wars were fought because of the British East India Company - in 1778, it had a private army of 67,000 soldiers, over 50% more than the total strength of the American militia at that time.