This essay surveys the changes and continuities in U.S. immigration law and policy between the Gilded Age and the 1990s–2010s. It points to how the administration of immigration law today is rooted in doctrines established in late nineteenth-century immigration cases. In particular, the essay connects current anxieties over immigration, borders, and national sovereignty to the “plenary power” doctrine that came out of the Supreme Court's decision in Chae Chan Ping v. United States (1889). Examining recent federal actions to “secure” the border and enforce immigration law, this essay begins to address the ways in which current policy continues to reflect Gilded Age anxieties about territory, sovereignty, migration, and diverse populations during an era of constantly shifting borders.