Reading democracy

I wonder when Edmund S. Morgan's book American Slavery, American Freedom made it into college reading.  The book was published in 1975 and among other things, argues that Virginia colonists were particularly sensitive to the issues of being free citizens because they owned slaves.  Thus slavery was an ingredient in the desire for independence from Britain?

Morgan's thesis is not of importance to me because I know that democracy came from the Vikings who settled much of England in the 11^th Century. Their descendants where the colonizers of the United States.