Although it is readily apparent that conservatism is united in its principled hostility to modern Progressive Liberalism, it is often more difficult to pin down just what the movement stands for. Johnathan O’Neill suggests that a focus on defending and preserving the Constitution could unite the otherwise fractious conservative movement. In this spirit, he examines four early conservative responses to Progressivism, all of which continue to have supporters today: Burkean traditionalism, Southern Agrarianism, libertarianism, and constitutional conservatism. While the first three had a strained, ambiguous, or hostile relationship to the constitutional order that limited their ability to respond to Progressivism, the latter offered informed and forthright resistance to Progressivism based on an affirmation of American constitutionalism. These conservatives met Progressivism with principled arguments rooted in the constitutional tradition, and they give us a historical example that can offer guidance to today’s conservatives.