The Civil War and Reconstruction periods in United States history are widely viewed as a “second founding” of the nation—one that sought to bring the American regime into better alignment with the aspirations articulated at the first founding. Among the figures involved in shaping this new start for the American republic, Lyman Trumbull played an instrumental role. As the chairman of the influential Senate Judiciary Committee, Trumbull advanced the most important legislation of both the Civil War and Reconstruction, including the First and Second Confiscation Acts, the Habeas Corpus Act of 1863, the 1866 Freedmen’s Bureau Act, and the Military Reconstruction Acts. Most significantly, he was the principal author and driver of the Thirteenth Amendment, which abolished slavery permanently throughout the United States. On the basis of the Thirteenth Amendment, he also authored the Civil Rights Act of 1866, the nation’s first civil rights law, which protected the fundamental rights of all Americans, regardless of race, color, or previous condition of servitude. Despite being arguably the greatest legislative architect of America’s second founding, Trumbull later turned his back on the Reconstruction that he helped initiate. Worried that Reconstruction was going too far and lasting too long, he eventually embraced a rigid and uncompromising view of states’ rights, rejecting his own previous defense of the national government’s ultimate power and responsibility to secure the privileges and immunities of US citizenship. Paul Rego’s study of Trumbull’s political and constitutional thought is a much-needed exploration of this key figure in Civil War and Reconstruction history. Like the framers of the first founding, Trumbull was complex and contradictory—a symbol of both the nation’s rebirth and its lost promise, as responsible for the period’s disappointments as he was for its triumphs. This is a long overdue book on one of the forgotten framers of the United States. Lyman Trumbull and the Second Founding of the United States examines the political and constitutional thought of Trumbull. Understanding Trumbull is essential to a comprehensive understanding of American political and legal development, especially during the Civil War and Reconstruction.