By presenting new work on the nineteenth century Americas, this session offers some preliminary answers. Eric Herschthal shows how enslaved and free people of color took advantage of Spanish slave codes and royal decrees to claim their freedom in the early nineteenth century. By acting on legal information circulating between Louisiana and New Spain, enslaved people stirred fears of slave revolt and Spanish meddling—and, in the process, helped to check the United States’ westward expansion. Alice Baumgartner looks at how the abolition of slavery in Mexico in 1837 had profound if forgotten consequences for the future of the institution in the territories that the United States would acquire from Mexico in 1848. Although most of the Mexican cession lay below 36o30’, even Northern Democrats who had supported the annexation of Texas without any restrictions on slavery were loathe to reestablish the “peculiar institution” where it had been abolished. Mexican law, in other words, was instrumental in destabilizing the fragile balance between North and South with respect to slavery. James Shinn argues that the Ten Years’ War—a nationalist rebellion in Cuba that lasted from 1868 to 1878—shaped how people in the United States understood sovereignty. Though metropolitan elites pointed to a de facto government as a sign of independence, Cuban rebels insisted that human rights concerns be taken into account when assessing claims to sovereignty. By showing how this vision was adopted by their allies in the United States, including African Americans and radical white Republicans, Shinn traces how the vernacular notions of sovereignty that developed in Cuba during the Ten Years’ War influenced internationalist thought in the United States. Taken together, these papers show that three of the most quintessentially “American” phenomena—westward expansion, sectional controversy, and the right to self-determination—were in fact shaped by ideas from Latin America.