This chapter analyzes different methodologies for using the history of international development and economic growth to study US foreign relations. Early efforts to historicize development, driven largely by the scholarship of anthropologists, political theorists, and historical sociologists, focused on the intellectual origins and discursive effects of development and growth discourse. I show how, over the past two decades, historians have expanded upon this work in multiple ways. They have used governmental and nonstate archival collections to analyze the intellectual and political origins of ideas about development and growth in the United States. They have used documents in foreign languages from across the world to analyze how those receiving development assistance alternately resisted, challenged, accepted, adapted, and integrated US foreign aid into their domestic state-building and development initiatives. Historians have likewise integrated analytic frameworks from other subfields and disciplines – such as environmental history, science and technology studies (STS), and the history of economic thought – to assess the short- and long-term legacies of development initiatives. The chapter explores these approaches to analyzing development and growth as entry points to study how, why, and to what ends the United States exercised power in myriad ways across the world.