This chapter traces the history of the Mexico—United States (US) —Central America triangle, attempts to explain why Mexican and US policies toward Central America have sometimes differed, and describes how these differences have hindered efforts to find lasting solutions to the region's problems. Mexico's foreign policy during the 1920s began to be one of solidarity with all of Central America. The chapter highlights the importance of the Pan American movement that developed under US leadership and the nature of Mexican and US foreign policy measures in response to the various Central American problems, from the early nineteenth century to the postwar era. It explores the evolution of the Central American foreign policy of each country since the nineteenth century, but when there were already signs of the problems that would induce both Mexico and the US to adopt specific postures and conduct in line with their emerging foreign policies.