1863 - The Emancipation Proclamation, issued by President Abraham Lincoln during the American Civil War, takes a major step toward abolishing slavery in the United States. The document liberated all slaves in the Confederate States and committed the United States to ending all slavery after the Civil War, a pledge fulfilled with the ratification of the 13th Amendment to the Constitution in 1865, which incorporated 4.5 million African Americans (14 percent of the population) into the U.S. citizenry. (Library of Congress)