The introduction presents the book’s thesis that races are “invented categories” and that “Caucasians are made and not born” (4). Jacobson provides the broad terrain on which he will make his exploration of the ways that racial designations have “framed the history of European immigration” (6) in the United States. These include shifting designations of “white” and “Caucasian” as well as more specific designations (Anglo-Saxon, Celt, Hebrew, Nordic, Mediterranean, etc.).

Jacobs breaks the history of whiteness in the United States into three periods. The first period begins with the US Naturalization Act of 1790, which limited naturalized citizenship to “free white persons.” Beginning in 1840, however, a massive wave of Irish immigration began, which led to new definitions of whiteness. The second period lasts from 1840 until 1924 when whiteness was divided into a hierarchy of smaller races within itself. The third period begins in the late 1920s onward when whiteness was “reconsolidated.”

Alongside these three historic periods are the book’s two premises: that race is central to European immigration and citizenship in the US and that race is cultural and political rather than natural.