The history of nativism in the United States has received considerable scholarly attention, yet the few systematic attempts to explain it have focused predominantly on psychological or economic causes. This article asserts that such explanations fail to address the crucial cultural dimension of the nativism issue, which must be analyzed through the prism of historical sociology. Specifically, this article argues that American nativism cannot be understood without reference to an “American” national ethnic group whose myth–symbol complex had developed prior to the large-scale immigration of the mid-nineteenth century. Without understanding this social construction, it is difficult to explain subsequent attempts to defend it. This article, therefore, does not seek to retrace the history of American nativism. Instead, it focuses on the period prior to 1850, when American nativism was in its infancy. It examines the development of an Anglo-American ethnicity during 1776–1850 and attempts to delineate its structure. This “American” complex of myths and symbols, with its attendant set of life-style images and narratives, is shown to conform to more generally models recently presented by theorists of ethnicity and nationalism. Finally, it is argued that American nativism may have exhibited a very different pattern if an “American” national ethnicity had not taken root.