West, The. In American history, the frontier (unsettled area) usually lay to the west of settled regions. For this reason, the terms west and frontier came to have the same meaning. To the first colonists, the frontier lay beyond the Appalachian Mountains. Later, pioneers who lived in the Midwest considered the plains and mountains farther west to be the frontier. See also Pioneer life in America ; Western frontier life in America ; Westward movement in America .