On Dec. 18, 1865, slavery ended in the United States. Secretary of State William Seward issued a statement verifying the ratification of the 13th Amendment to the U.S. Constitution making the end of slavery official eight months after the end of the Civil War.The amendment states:n Dec. 18, 1865, slavery ended in the United States. Secretary of State William Seward issued a statement verifying the ratification of the 13th Amendment to the U.S. Constitution making the end of slavery official eight months after the end of the Civil War. The amendment states: