The Frontier refers to the expanding boundary of settled land in the United States during the 19th century. It represented the edge of civilization, where pioneers moved westward in search of new opportunities, land, and resources. This movement was driven by the belief in Manifest Destiny, the idea that Americans were destined to expand across the continent. The concept of the Frontier is closely associated with the American West, which includes states like California, Texas, and Oregon. It played a significant role in shaping American culture, identity, and history, influencing literature, art, and the development of towns and cities.