Frederick Jackson Turner,
The Frontier in American History…
(1921)
“ The relation of the Provinces of the Lake and Prairie Plains to the rest of the United States is an important element in the significance of the Middle West. On the north lies the similar region of Canada: the Great Lakes are in the center of the whole eastern and more thickly settled half of North America, and they bind the Canadian and Middle Western people together. On the south, the provinces meet the apex of that of the Gulf Plains, and the Mississippi unites them. To the west, they merge gradually into the Great Plains ”
