Writing the Foundation trilogy, Asimov based the idea of a declining empire on Edward Gibbon's The History of the Decline and Fall of the Roman Empire (1776-1789). Because of this the trilogy is often read as re-enacting the fall of the Roman Empire on a galactic scale. In this paper I contend that while the fall of the Roman Empire is the initial model, aspects of American expansionism come to dominate the narrative as soon as there is a need for something to replace the falling order. By following the development of the trilogy, and by drawing parallels to American ideological and political history, J will show how the novels are shaped by frontier thematics and the idea of manifest destiny. Because the trilogy portrays large swaths of future history through archetypal hero figures, my focus, too, will be on some of the main characters. The prominence of frontier thematics in the trilogy, as well as the appearance of historical models other than the Roman Empire, have gone largely unnoticed because of Asimov's own explanations of using Gibbon's History (1) as a model (In Memory 311). Although the "harsh frontier existence of the Foundation" (DiTommaso 272) has occasionally been mentioned, what this notion really entails has yet to be explored. (2) Instead, the trilogy has often been studied from a more philosophical or ideological angle, giving rise to discussions on imperialism, determinism and utilitarianism (Candelaria, Moore, and Miller, respectively). Asimov himself was always quick to dismiss the possible American parallels in his work as uninteresting, and simply resulting from his American cultural background and exposure to pulp fiction (Wojtovicj, Ingersoll 73). It may be obvious that Asimov's work is a product of his cultural background, and even more importantly of the early 20th-century pulp magazines and John W. Campbell's editorship of Astounding Science Fiction (In Memory 201, Campbell Letters 20). Yet this background is more important than is generally acknowledged, in part because it reveals the American parallels on which the whole work is based.