There is no "frontier " country. Usually a frontier is an unsettled area that is part of a country.
It was called the New Frontier.
The New Frontier.
. . . New Frontier.
The New Frontier.
Kennedy's new plan was called the New Frontier, promising equality, employment and aid to the poor.
new frontier
The region of a country bordering on another or a line, barrier, etc., marking such a border is called a frontier. A frontier is also the edge of the settled area of a country.
the lost frontier
The New Frontier.
The New Frontier.
The New Frontier.
The New Frontier.