By the mid-19th century, America’s westward expansion, along with a growing abolition movement in the North, would provoke a great debate over slavery that would tear the nation apart in the bloody American Civil War (1861-65). Though the Union victory freed the nation’s 4 million slaves, the legacy of slavery continued to influence American history, from the tumultuous years of Reconstruction (1865-77) to the civil rights movement that emerged in the 1960s, a century after emancipation.