A frontier is the political and geographical areas near or beyond a boundary. The term came from French in the 15th century, with the meaning "borderland"—the region of a country that fronts on another country.
The word "frontier" also means a region at the edge of a settled area, especially in North American development. It is a transition zone where explorers, pioneers and settlers were arriving. That is, as pioneers moved into the "frontier zone", they were changed by the encounter. A frontier can also be referred to as a "front".
That is what Frederick Jackson Turner calls "the significance of the frontier." For example, Turner argues that, in United States' 1893, one change was that unlimited free land in this zone was available, and thus offered the psychological sense of unlimited opportunity. This, in turn, had many consequences such as optimism, future orientation, shedding of restraints due to land scarcity, and wastefulness of natural resources.