邊陲理論乃騰納於一八九三年開始提出的一系列論文；旨在強調西部拓荒環境對美國歷史的重要性。騰納認為西部拓荒環境孕育出美國的個人主義、民主制度及國家主義；拓荒者不受傳統與權威的束縛，與大自然搏□，養成獨立自主、堅毅不拔等特殊的國民性格。由於邊陲理論鼓動國家主義，因此受到一般民眾與學者的歡迎。直到三○年代以後，才漸有反對的意見提出，在學術界上引起頗多爭論。
　　本文除探究其理論基礎，勾劃美國國民性格的特色外，並從歷年學者的批評中，討論其理論的缺失。說明騰納之所以被誤認為環境決定論者，乃在於其論點忽略歐洲文化遺產與東部城市文化的影響。論述騰納以經濟的觀點詮釋歷史的方法與其研究方法，並從中發現「遼闊開放的土地」亦是現代社會科學家研究美國國民性格的依據。逐一修正拓荒者影響美國性格形成的內容，並例舉歷史學家和行為科學家的研究成果，證明在美國國民性格的形成歷史中，邊陲理論佔重要的一席。

　　The hypothesis advanced in Frederick Jackson Turner's famous 1893 essay, "The Significance of the Frontier in American History," has been debated by many scholars. Turner's belief -- "the frontier is the line of most rapid and effective Americanization," -- suggested that the pioneering experience accounted for some of the distinctive characteristics of the American people.
　　The stress on general ideas and the highly intellectual quality of Turner's writings perplex some of his readers, for these subjects seem to lead themselves to a dramatic and romantic treatment. With this romantic aura, the Frontier Thesis received enthusiastic endorsement until the Depression. Yet, criticism arose to attack its untested ideas, its ignoring of the European cultural heritage and its neglecting of the influence of Eastern urbanization.
　　Though Turner did not deny the influence of the European social heritage, he underestimated its persistent strength. Probing his methodology and presenting the results of modern research in history and the behavioral science, this thesis tries to verify and modify the idea that the frontier influences the formation of American character, especially centering on the idea of 'free land.' As a result, Turner Thesis is in some ways a valid one; some of American mental traits are traceable to the frontier heritage.