Answer:
The American frontier includes the geography, history, folklore, and cultural expression of life in the forward wave of American expansion that began with English colonial settlements in the early 17th century and ended with the admission of the last remaining western territories as states in 1959.
Step-by-step explanation:
This era of massive migration and settlement was particularly encouraged by President Thomas Jefferson following the Louisiana Purchase, giving rise to the expansionist philosophy known as "Manifest Destiny".