After the U.S.-Mexican War, the Californio people, recent Mexican citizens, engaged with their new American surroundings by drawing on the long history of liberalism in Latin America. Having recently left the shadows of Spanish colonialism, Latin America and the northern parts of Mexico included developed local varieties of liberal ideology. As such, the Californios brought their uniquely local brand of liberalism to bear on American ideas about race, local infrastructure, immigration, and the rights of Native Americans. Drawing upon memoirs, speeches, newspaper articles, and interviews, this dissertation demonstrates that the Californios used Mexican liberal traditions to both conflict with and support American political and cultural shifts in the periods before and after the Civil War. By focusing on the historical traditions of Mexican liberalism, this dissertation expands the perspective on the Californios to consider their ideologies. This dissertation outlines a case of ideologies continuing to exist among the Californios after the U.S.-Mexican War in the second half of the nineteenth century.