The beginning of the controversy: Statement of the frontier thesis ; Later explanations and developments / Frederick J. Turner ; Turner's views challenged / George W. Pierson -- The frontier as safety valve drawing excess wage earners from the East: Not even an indirect safety valve attracting eastern farmers Fred A. Shannon ; A resources and sociopsychological safety valve / Ellen von Nardroff -- Democracy as a product of the frontier: Democratic practices of English origin / Benjamin F. Wright ; American democracy distinguished from democracy in general / John D. Barnhart ; The impact of the frontier : a case study / Merle Curti -- Influence of the frontier on American character: The significance of continuity / Earl Pomeroy ; Mobility a strong influence / Everett S. Lee ; The role of abundance / David M. Potter -- Summary: The thesis disputed / Richard Hofstadter ; The thesis upheld / Harry C. Allen.