This study examines U.S. national identity in the first third of the twentieth century. During this period, heated discussions ensued throughout the country regarding the extent to which the door of American society should be open to people of Mexican descent. Several major events brought this issue to the foreground: the proposed statehood of Arizona and New Mexico in the early twentieth century, the increase in Mexican immigration after World War I, and the repatriation of Mexican immigrants in the 1930s. The "Swinging Door" explores the competing perspectives regarding the inclusion or exclusion of people of Mexican descent embedded within each of these disputes.

This dissertation argues that four strategies evolved for dealing with newcomers of Mexican descent: assimilation, pluralism, exclusion, and marginalization. Two strategies, assimilation and pluralism, permitted people of Mexican descent to belong to the nation so long as they either conformed to an Anglo American identity or proclaimed a Spanish American one rooted in a European heritage, whiteness, and a certain class standing. Exclusion denied entry into the U.S., or in the case of those already there, no role in society. Marginalization, which became the predominant strategy by the 1930s, allowed people of Mexican descent to remain physically within the country so long as they stayed only temporarily or agreed to accept a subordinate status as second-class Americans. The prevailing view changed depending on the economic and political power of people of Mexican descent, their desire to incorporate as Americans, and the demand for their labor or land by other Americans.

One of the most significant findings of this project is that as the marginalization strategy gained adherents, the image of Mexican immigrants as temporary workers or "guestworkers" became the primary way in which Americans, Mexicans, and the immigrants themselves regarded the newcomers from Mexico. Despite the fact that this image was often false, the notion of Mexicans as only temporarily in the U.S. proved too seductive for the many divergent voices to resist as this image theoretically allowed Mexicans to enter the country and to provide their labor without threatening extant notions of American identity.