It has been calculated that the whites advance every year a mean distance of seventeen miles along the whole of this vast boundary. Obstacles such as an unproductive district, a lake, or an Indian nation are from time to time encountered. The advancing column then halts for a while; its two extremities curve round upon themselves, and as soon as they are reunited, they proceed onwards. This gradual and continuous progress of the European race towards the Rocky Mountains has the solemnity of a providential event; it is like a deluge of men rising unabatedly, and daily driven onwards by the hand of God.

—Alexis de Tocqueville, Democracy in America