The Thirteenth Amendment to the United States Constitution made slavery and involuntary servitude illegal, except as punishment for a crime. The amendment was passed by the Senate on April 8, 1864, by the House of Representatives on January 31, 1865, and ratified by the required 27 of the then 36 states on December 6, 1865, and proclaimed on December 18, 1865. It was the first of the three Reconstruction Amendments adopted following the American Civil War.