Early in the twentieth century, a subset of American Protestants began to tour the globe. They also built international NGOs and created new connections with their fellow believers in Europe, Asia, Africa, and Latin America. In the process, these ecumenical Protestants -- sometimes called "liberal" or "mainline" Protestants -- transformed American domestic politics from the 1920s to the 1960s. Inspired by its global connections, this influential religious community helped create the United Nations and the Universal Declaration of Human Rights, and it mobilized politically in support of the New Deal, the Civil Rights Movement, the Great Society, and anti-Vietnam War protests. In the same way that the rise of the Christian Right cannot be understood apart from the mobilization of evangelicals, the rise of American liberalism at mid-century cannot be understood without a historical account of the global political mobilization of American liberal Protestants.