This chapter examines the rise and evolution of the liberal order that was created by the United States and and other liberal democratic states in the decades after World War II, along with the modern challenges to it. The liberal order that emerged after World War II paved the way for a rapid expansion in world trade, the successful integration of former enemies such as Japan and Germany, and the transition to liberal democracy in formerly authoritarian states. Furthermore, the collapse of communism was considered a triumph of liberalism. The chapter first explains how the American liberal order was constructed after World War II before discussing the successes of that order and the end of the ‘socialist’ project in the 1980s. It also analyzes some of the major threats to this liberal order today, particularly those from within, as a result of Donald Trump’s rejection of the American liberal tradition.