This article examines the claims that the American archival profession owes its existence to the unique combination of a "historical manuscripts tradition" and a "public archives tradition" over the course of the nineteenth and twentieth centuries. It also evaluates the differences and similarities between the traditions' theories of practice and ideologies in early twentieth century American writings on archives and the Society of American Archivists' "basic manuals" that defined much professional theory and practice in the late twentieth century. These findings have contemporary implications, as those seeking to define modern archival theory often erroneously use the origins of the American archival profession to support their arguments. (Contains 88 notes.)