This dissertation offers a comparative historical analysis of the role of the state in shaping nationalist sentiment in Hawai'i, Alaska, and Puerto Rico during the twentieth century. There are active separatist movements within the three territories, yet there is important variation among them in terms of rationale, organization, and goals. More specifically, the Hawaiian Sovereignty Movement draws on ethnic dimensions of nationhood to pursue greater self-determination. By contrast, the Alaskan Independence Party evokes civic rhetoric to justify secession. The case of Puerto Rico independistas is characterized by a hybrid of ethnic and civic sentiment, where being Puertorriqueño is simultaneously a heritage and a political orientation. I explain such differences as a result of United States federal legislation throughout the process of incorporation. From the moment a territory is annexed, various policies are directed at organizing and integrating the new populations. As a latent effect, these policies both reinforce the status of the territory and its residents (vis-à-vis the American populace) and grant disparate privileges within the territory's population. In turn, these dynamics shape a collective identity that coalesces around separatism. Using archival materials, I focus on status legislation, land rights, and language, illustrating how policy in these arenas created the rationale and rhetoric for subsequent separatist movements. My research contributes to understanding how identity and legislation, nation and state, are mutually constituted.