This book traces the history of American constitutionalism, from the Republic's founding through the civil rights revolution of the 1960s and the current crisis of neoliberal governance. It vigorously asserts the primary role of the American people's constituent power in shaping constitutional norms and positive law. Professor Ackerman precisely reconstructs historical-constitutional moments, born from intense class struggles and social antagonism, where the voice of the people imposed itself through institutional shifts and legal innovations. Key turning points like the founding against colonial rule, the Civil War, the New Deal, and the civil rights movement fundamentally altered the nation's constitutional pact, inaugurating new political and legislative cycles and demonstrating the constituent power against usurpation.