Mae M. Ngai in “Architecture of Race in American Immigration Law,” argues that immigration legislation based on nation-states and race was “key to its [the United States] modern persona.” Ngai breaks her argument into three main subject areas: “Invention of National Origins,” “Eligibility to Citizenship and the Rule of Racial Unassimilability,” and “From Conquered Natives to Illegal Aliens.”

In the first section, Ngai describes how the federal government came up with the quota system used in the Immimgration Act of 1924. She points out the many flaws in its methodologies including a study by the Census Bureau in 1909 called A Century of Population Growth during which the surnames of families listed in the 1790 census were analyzed for nationality. The study concluded that 82% of families listed in the 1790 census were of English descent but this was found to be inaccurate after statisticians realized that many Irish and German immigrants anglicized their last names. The census redid their study in 1928 and the percentage of families from England was reduced down to 67%. 

In the second section, Ngai points out that there are two elements of 20th century racial ideology: the legal definition of white and the rule of racial unassimilability. Ngai also points out that the eligibility of southern and eastern european immigrants to become citizens was never questioned, while the eligibility of other undesirable non-white races was. Three court cases are layed out in this section: Ozawa v. United States (1922), United States v. Thind (1923), and Terrace v. Thompson (1923). The first two cases set important precedents related to the ineligibility of non-white immigrants to be citizens, and Terrace v. Thompson ruled that alien land laws fell within state police power and that the alien land laws did not discriminate against solely Japanese because it applies to all aliens regardless of race. 

Finally, the third section specifically discusses the position of Mexicans within American society in the early 20th century. Ngai discusses how Mexicans were conquered when their native southwest was ceded to the U.S. after the Mexican-American war, but then made synonymous with illegal immigration. Ngai concludes her discussion of Mexican immigrants by describing the development of commercial agriculture and the impersonal relationship between absentee landowners and migrant laborers.