From 1900 to 1945, well before the consolidation of area studies, U.S. scholars in the humanities and the social sciences delineated the contours of a recently "rediscovered" land: South America. Their publications provided comprehensive and empirically informed visions of the subcontinent that contributed to the United States' diplomatic rapprochement with the region. Parallel to business prospectors, Pan-American enthusiasts, religious missionaries, and travelers, a group of U.S. scholars came to the region in search of new data and fresh, direct observations to confirm or reject prior generalizations and ste reo types. Little by little, their authoritative repre sen ta tions began to fill the previous vacuum of knowledge, said to represent a major obstacle for more intense economic relations between the two Americas. Enhanced knowledge, the argument ran, would generate greater mutual trust in inter-American relations. These acts of knowing laid the foundations for a substantial apparatus of knowledge in the ser vice of hemispherism.I call these scholarly engagements "disciplinary interventions": disciplinary because they were rooted in scientific disciplines; interventions because they fostered U.S. economic, technological, and cultural hegemony in the region. In a way, these adventures in disciplinary knowledge constituted a continuation of U.S. hemispheric diplomacy through other means. In a region free from direct U.S. military and po liti cal intervention, information gathering southern republics. Disciplinary Conquest deals with the parallel and complementary expansion of the U.S. informal empire and the formation of regional knowledge about South America. Increased commercial and investment opportunities in South America motivated these scholars to extend disciplinary research into this new and unexplored territory. Interest in Inca citadels developed into a full-blown inquiry of Andean archaeology. A geo graph i cal survey along the 73rd meridian provided the initial step for the project of South American geography. Interest in the administration of the Spanish colonial system and in U.S.-Latin American diplomatic history served to configure the field of Hispanic American history. In areas as different as geography, government, social relations, economics and finance, education, and history, scholars made a concerted effort to survey, report, and interpret the complex realities of the region, comparing them with Eu rope, the United States, and former Iberian empires.My claims refer specifically to the period 1900-1945, which corresponds to the construction of Pan-American institutions and ideals. 2 Before 1900, the very rarity of specialized regional knowledge made the interaction between knowledge and state power less frequent and effective. First proposed by Secretary of State James G. Blaine in 1881, the Pan-American ideal was envisioned as a loose cooperative union of the American republics. 3 Later, under President Woodrow Wilson, as the U.S. launched a rapprochement with South America, the notion...