Liberalism has long been a central factor in U.S. politics, going back at least to the New Deal and continuing through the Great Society of the 1960s and the social justice and environmental movements of today. As a social and political ideology, liberalism emphasizes the democratic ideals of anti-authoritarianism, the equality of all peoples, the rule of law, and democratic governance through regular elections and civil participation. Liberals generally accept that social progress entails a contest among differing ideas and beliefs, for the betterment of all. Liberal principles have lain behind many Democratic presidencies, from Franklin D. Roosevelt’s to Bill Clinton’s to Barack Obama’s and Joe Biden’s terms in office. And yet liberalism, long subject to criticism by conservatives, has lately suffered significant setbacks in U.S. politics, even as it continues to enjoy broad support among the American populace. How has liberalism been informed by its past, and what is the best path forward for its supporters in the twenty-first century? Covering key moments and ideas from previous eras to today, this work explores this all-important thread in American political culture and how it has impacted the workings of government, the economy, national defense, international relations, law and society, domestic programs, and cultural values throughout U.S. history. The documents contained within these sections provide an overview of the history and significance of conservatism in American society, exploring key milestones in the movement’s development from the days of the Founding Fathers to the modern era.