This chapter looks at the history of US citizenship and immigration law and argues that denying admission or citizenship status to certain groups of people is closely correlated to a denial of whiteness. On this account whiteness is not a fixed or natural concept, but instead is a social construction whose composition changes throughout time and place. Understanding whiteness in this way allows one to see how white supremacy is not limited merely to instances of racism or ethnocentrism, but can also include instances of xenophobia. On this account, whiteness is more analogous to a braid of three interwoven strands: the racial strand (e.g., science, biology, or phenotypes), the ethnic strand (e.g., culture, customs, or heritage), and the national strand (e.g., territory, sovereignty, and citizenship). In emphasizing one or a combination of these strands, whiteness can be granted to social groups that previously were denied full white status, while at the same time it can be rescinded from groups that at different times and different places might have been considered (if only provisionally) white. Understanding whiteness in this way is important for dealing with issues of immigration and citizenship because it lets us see how nationality and xenophobia play a role in the construction of whiteness and thereby how terms like illegal help to reify the status of certain persons, including natural born citizens, as perpetual foreigners (i.e., non-whites).