I agree with others that brought up the era of indentured servitude, which brought many "poor whites" to America pre-Revolution. This was most of the cheap labor force prior to largely being displaced by African chattel slavery post-Revolution, and created a kind of "poor white" class in competition with African Americans. Meanwhile, the Puritan North (which had just finished the English Civil War against the Virginia-settling Cavaliers) were more merchants/family farmers/industrialists not so dependent on cheap labor. The ensuing divisions between US whites (ie North vs South) stem from these "initial conditions". Its all in "American Nations" by Colin Woodard.