Introduction
The physical frontier is the physical, geographical boundary of our nation. The initial frontier was set at the "back country" regions of young American villages and cities such as Jamestown and Plymouth in the 1600s. Now, in the 21st century, the frontier is set as outer space at various space programs, such as NASA, are attempting to colonize celestial bodies, with focus on the moon and Mars. In this segment, the evolution and progression of the frontier throughout the years will be analyzed.