Frederick Jackson Turner,
The Frontier in American History…
(1921)
“ In American thought and speech the term "frontier" has come to mean the edge of settlement, rather than, as in Europe, the political boundary. By 1690 it was already evident that the frontier of settlement and the frontier of military defense were coinciding. As population advanced into the wilderness and thus successively brought new exposed areas between the settlements on the one side and the Indians with their European backers on the other, the military frontier ceased to be thought of as the Atlantic coast, but rather as a moving line bounding the un-won wilderness. ”
