History of the 13th Amendment
In 1784, a Congressional Committee led by Thomas Jefferson drafted the Northwest Ordinance, laying out the boundaries and initials laws for new states to be formed in new territories. The final version omitted the key provision that abolished slavery in the U.S. (download 1784)
In 1787, Congress passed a revision to the 1784 Ordnance and included language to abolish the private ownership of slaves in the new territories (download 1787):
“There shall be neither slavery nor involuntary servitude in the said territory, otherwise than in the punishment of crimes, whereof the party shall have been duly convicted…”
In January 1865, after a contentious debate in Congress, the 13th Amendment was passed and subsequently ratified by the States in December 1865.