organization formed on May 14, 1863, by Susan B. Anthony (Anthony, Susan B.) and Elizabeth Cady Stanton (Stanton, Elizabeth Cady) that sought to end the American Civil War through an amendment to the U.S. Constitution that abolished slavery. To this end they organized a Mammoth Petition that urged Congress to emancipate all slaves. Headed by Stanton, the league claimed some 5,000 members, many of whom were suffragists who had suspended work on woman suffrage to concentrate on the war effort. Widely praised for its work, the group collected some 400,000 signatures. In 1865 the Thirteenth Amendment, which abolished slavery, was enacted. With the amendment's passage, the league disbanded, and women, armed with valuable experience in organizational planning and public speaking, returned to the battle for suffrage.