On this day 150 years ago, December 18, 1865, then Secretary of State William H. Seward issued the following statement verifying the ratification of the 13th Amendment.
These two digitized images come from A Century of Lawmaking. The image below comes from the Abraham Lincoln Papers at the Library of Congress and shows that the Joint Resolution submitting the 13th Amendment to the states was signed by Abraham Lincoln and Congress:
For more on how the 13th Amendment has been interpreted by the U.S. Supreme Court, see the section on the 13th Amendment in the Constitution Annotated on Congress.gov. If you are interested in learning more, the Library of Congress has a Web Guide to the 13th Amendment.