The Northwest Ordinance
The population of the United States was like a body of water that was being steadily enlarged by internal springs and external tributaries. It was augmented both from within and from without, from natural increase and from immigration. It had spread over the whole coast from Maine to Georgia and slowly back into the interior, at first along the lines of river communication and then gradually filling up the spaces between until the larger part of the available land east of the Alleghany Mountains was settled. There the stream was checked as if dammed by the mountain barrier, but the population was trickling through wherever it could find an opening, slowly wearing channels, until finally, when the obstacles were overcome, it broke through with a rush.

Twenty years before the Revolution the expanding population had reached the mountains and was ready to go beyond. The difficulty of crossing the mountains was not insuperable, but the French and Indian War, followed by Pontiac's Conspiracy, made outlying frontier settlement dangerous if not impossible. The arbitrary restriction of western settlement by the Proclamation of 1763 did not stop the more adventurous but did hold back the mass of the population until near the time of the Revolution, when a few bands of settlers moved into Kentucky and Tennessee and rendered important but inconspicuous service in the fighting. But so long as the title to that territory was in doubt no considerable body of people would move into it, and it was not until the Treaty of Peace in 1783 determined that the western country as far as the Mississippi River was to belong to the United States that the dammed-up population broke over the mountains in a veritable flood.