When launching the Alliance for Progress in 1961, John F. Kennedy promised that this new development program would transform Latin America into a community of modern, prosperous, and politically stable allies. Yet, when Richard Nixon ended the program ten years later, there was more evidence of broken promises, political coups, and covert military operations than of transformative cooperation. Sandwiched between Kennedy’s and Nixon’s presidencies, Lyndon Johnson’s marked a transformative era in inter-American relations as Johnson and his chief inter-American aide, Thomas C. Mann, struggled to deliver on their predecessors’ bold promises while grappling with the demands of Cold War national security. In this first in-depth study of Johnson, Mann, and Latin America in the 1960s, Thomas Tunstall Allcock provides a nuanced and balanced assessment of two often maligned yet hugely influential policy makers during this vital period. In demonstrating that Johnson and Mann were New Dealers, keen to operate as good neighbors and support Latin American development and regional integration, Tunstall Allcock illuminates the difficulties faced by US modernization efforts. Ranging from domestic challenges from both right and left to a series of military and political crises including riots in the Panama Canal Zone and the threat of “another Cuba” in the Dominican Republic, these difficulties would be handled with wildly varying degrees of success. In Tunstall Allcock’s account, Johnson and Mann emerge as complex, rounded figures struggling to overcome a host of challenges and their own limitations even as the flaws and shortcomings of US policy are laid bare.