How has the American frontier evolved - what geographical obstacles have Americans faced when moving toward the frontier?

The American frontier has evolved at a fast rate

Explanation:

A frontier is characterized by a part of land or space occupied by two or more person over the course of some miles.

The American frontier has evolved at a fast rate from the early 1800s up until now. The ever increasing desire of America to gain ore land and enlarge it coasts has led to many of its citizens emigrating westward through out the course of the 1800s. But then there has been some geographical obstacles faced by Americans during their westward movements, these are the alleghany mountains, the Mississippi, and Missouri.

The American frontier has evolved at a fast rate