Here we have four case studies from North America, Central America, and South America to assess the links between peaceful borders and the occurrence and proliferation of illicit transnational flows. All the borders involved are peaceful with important variation across the cases in terms of historical background and trajectories. First, we study the North American Borders (US-Canada and US-Mexico), especially in the period since the establishment of NAFTA in 1994. Second comes the Northern Triangle of Central America, which includes the borders of Guatemala, El Salvador, and Honduras since the end of the civil wars in the early 1990s. Third, we turn to the Colombian borders with Venezuela, Ecuador, Peru, and Brazil, with a particular focus on the last twenty years that witnessed the tensions between Colombia, Ecuador, and Venezuela, and the long civil war that involved Colombia and the FARC until 2016. Finally, we analyze the Tri-Border Area of the Southern Cone of South America, which includes the borders of Argentina, Brazil, and Paraguay, especially since the establishment of MERCOSUR in 1991.