Expansion of the western frontier exploded during the Civil War when Southerners fled their war-torn states- this statement is false.
Step-by-step explanation:
Native Americans were not happy with the immigration of others settler into their territory. They possess some different thought about how to handle them. The Medicine Lodge creek treaty was an attempt that was taken by the U.S government for the peaceful movement of Native Americans to reservations.
Crack down on plain of General Sharma was done by Satanta's Warren Wagontrain Raid .Expansion of the western frontier does not have any relation with the expedition or initiation of civil war of America. Southern states were not much affected by the immigrants influx.