This thesis explores the origins and operation of international adjudication projects in the Americas. Part 1 centres on the codification of dispute settlement mechanisms pursued by American states during the first part of the 20th century in regional treaties. It argues that, contrary to established views, these regional treaties were not just about peace; instead, states used them to promote diverse and sometimes contradictory goals. Latin American states aimed to curb US power in the region and to project themselves as civilized nations. The United States by turns adopted a bystander role or attempted to block more sovereignty-constraining proposals. After intense contestation, American states concluded two treaties to organize peace in the postwar world. The Rio Treaty was a defence pact with an autonomous enforcement mechanism, to which the United States was strongly committed. The Pact of Bogotá reflected Latin American states’ views that a comprehensive legal framework for solving disputes, featuring mandatory recourse to the International Court of Justice (ICJ), would mitigate regional power differentials. Part 2 accounts for the uneven use of these treaties, as American states invoked the Rio Treaty frequently during the Cold War and the Pact of Bogotá lay dormant until 1986. The Rio Treaty’s vague provisions facilitated its early dominance, and the treaty’s mechanisms functioned as an adjudicatory body for disputes between American states. The turn to the ICJ can be explained by the decay of the Organization of American States, shifts in Latin American states’ foreign policies, and the increased professionalization of international law. Overall, this thesis disrupts links between adjudication and peace, Eurocentric histories of international adjudication, and judicial-centric views of international law.