At least since Tocqueville, American legal practices and institutions have been seen as different in key respects from those of both England and continental Europe. Within this three-way comparison, evident Anglo-American differences diverted the search for the origins of U.S. legal culture away from explanations rooted in the common law tradition. It is widely accepted that the distinguishing features of American legal institutions, beginning with the primacy of adjudication within the administrative process, and continuing with the emphasis on juries and litigants in court procedure, closely correspond with key common law principles. Nonetheless, the prominent line of explanation, evident in Robert Kagan’s work on American adversarial legalism, has highlighted elements intrinsic to American political structure and history as explanation for trans-Atlantic institutional differences. This paper argues that notwithstanding differences between England and the United States, common law ideology and institutions played a crucial role in the creation of a distinct administrative state model in the United States. The paper accounts for the divergence between England and the United States through the fact that in England the common law has long competed with countervailing continental legal and political traditions. Common law ideology existed across key junctures of English history as an oppositional ideology aimed at curtailing perceived abuses of the king’s prerogative, and later parliamentary social legislation. Once we view the common law’s role in England through this oppositional lens, it becomes easier to see how and why common law ideology might explain distinctive elements of American legal culture, not only vis a vis continental Europe, but England as well. With this goal in mind, the paper draws on key works in English legal history to explain the coexistence of competing common law and continental legal ideologies in England over time, and the implications of this struggle where both similarities and differences between England and the United States are concerned. With this history in place, the role of legal traditions in the creation and persistence of contemporary differences between American and European legal cultures can come into clearer view.