The hypothesis advanced in Frederick Jackson Turner's famous 1893 essay, The Significance of the Frontier in American History, has been debated by three generations of scholars. The pioneering experience, Turner suggested, accounted for some of the distinctive characteristics of the American people: during three centuries of expansion their attitudes toward democracy, nationalism and individualism were altered, and they developed distinctively American traits, such as wastefulness, inventiveness, mobility, and a dozen more. After opening with a summary of the appearance, acceptance, and subsequent dismissal of the theory, the author carefully defines the "frontier" and reviews recent evidence on its political, social, and economic characterstics. He discusses the compulsion to migrate and examines other behavioral patterns and traits in his explanation of how and why pioneers moved west. His extensive bibliographic notes constitute a remarkable guide to the literature of many disciplines dealing with the frontier concept.