This article examines trajectories of nationalism in 20th century Argentina, Mexico, and Peru through the analytical lens of schooling. I argue that textbooks reveal state-sponsored conceptions of nationhood. In turn, the outlooks and practices of teachers provide a window for understanding how state ideologies were received, translated, and reworked within society. During the late 19th century, textbooks in Mexico, Argentina, and Peru conceived of the nation as a political community, emphasized ???civilization??? for achieving national unity, and viewed elites as driving national history. During the 20th century textbooks eventually advanced a cultural understanding of the nation, envisioned national unity to be achieved through assimilation into a homogeneous national identity, and assigned historical agency to the masses. Yet, teacher responses to these changes varied. In Mexico under C??rdenas (1934-1940), teachers predominantly embraced textbooks that promoted a popular national culture. By contrast, teachers in Argentina under Per??n (1946-1955) and in Peru under Velasco (1968-1975) largely opposed the new texts.