Whiteness is not biological but, instead, a constructed social category that gains authority in its racialization. This racialization is fluid, constantly shifting its definition, and open to different legal and political interpretations.

While whiteness is explicitly cited as a condition for naturalization and, thus, citizenship in the 1790 Citizenship Act, it was not actually defined in this act. While this prerequisite whiteness appears extremely exclusive today, Jacobson draws attention to what was experienced as its inclusivity at the time of the act’s passage and through the early 20th century: This condition of whiteness did not require that immigrants be Anglo-Saxon or British and thus allowed for a wide variety of legal interpretations of just what whiteness was. This set the stage for 175 years of shifting definitions of whiteness that Jacobson explores.

While the 1790 Naturalization Act only cited a generic whiteness, in the 19th century, scientists argued that there were distinct white racial groups across whiteness. By the mid-19th century, science shifted from mere categorization of racial groups to an explicit hierarchization of them. While current understandings of the scientific investment in race have focused on “scientific racism,” which hierarchized by way of false racializations that society continues to recognize, the hierarchies of distinct white races were also considered scientifically authoritative and biologically based: What we now think of as ethnicity was considered race.