The Pristine Myth: The Landscape of the Americas in 1492
William M. Denevan
Department of Geography, University of Wisconsin, Madison, WI 53706
Abstract. The myth persists that in 1492 the Americas were a sparsely populated wilderness, -a world of barely perceptible human disturbance.- There is substantial evidence, however, that the Native American landscape of the early sixteenth century was a humanized landscape almost everywhere. Populations were large. Forest composition had been modified, grasslands had been created, wildlife disrupted, and erosion was severe in places. Earthworks, roads, fields, and settlements were ubiquitous. With Indian depopulation in the wake of Old World disease, the environment recovered in many areas. A good argument can be made that the human presence was less visible in 1750 than it was in 1492.
http://jan.ucc.nau.edu/~alcoze/for398/class/pristinemyth.html
And but for the evil white man, who reintroduced the horse (in its domesticated version) the noble red man would have also wiped out the buffalo. That's because only then were they able to hunt individual buffalo rather then use their prior method of hunting large mammals - stampeding entire herds of them over cliffs or bluffs.
A good argument can be made that the human presence was less visible in 1750 than it was in 1492.
The continent was still mostly unpopulated in 1750.
Coronado marched across the great plains, from Colorado to the Mississippi in a fairly early Spanish explortion in 1540.
Yes, there were populations in the East and West.
And the point is?
The center of the continent was a vast, unpopulated wasteland (they saw one band of less than 10 Apaches whose only domesticated animals were dogs in a couple of thousand miles of travel across the plains.