The treaty that formalized the end of the U.S. Civil War was the Treaty of Appomattox Court House, signed on April 9, 1865. This agreement marked the surrender of Confederate General Robert E. Lee to Union General Ulysses S. Grant, effectively bringing an end to the war in the Eastern Theater. The terms were generous, allowing Confederate soldiers to return home with their horses and sidearms, facilitating reconciliation. This event symbolized the collapse of the Confederacy and the preservation of the Union, leading to the Reconstruction era, which aimed to address the complex challenges of reintegrating Southern states and ensuring rights for formerly enslaved people.