To understand Lincoln’s legacy is to understand the modern American state. He fundamentally redefined the relationship between the federal government and the individual. Before Lincoln, the United States was often referred to in the plural; after Lincoln, it was an inseparable union. He demonstrated that a democracy could withstand the most extreme internal pressure, provided its leadership remained committed to the core principles of equality and justice. He expanded executive power in ways that were unprecedented but necessary for the survival of the nation. By championing the abolition of slavery, he turned the U.S. Constitution from a document of compromise into a beacon of human rights. This chapter analyzes how his presidency set the stage for all that followed, establishing the precedents that would guide the nation through the crises of the 20th century and beyond.