1777: Constitution of the Vermont Republic bans slavery. 1780: Pennsylvania passes An Act for the Gradual Abolition of Slavery, freeing future children of slaves. Those born prior to the Act remain enslaved for life. The Act becomes a model for other Northern states. Last slaves freed 1847. 1783: Massachusetts Supreme Judicial Court rules slavery illegal based on 1780 state constitution. All slaves are immediately freed. 1783: New Hampshire begins a gradual abolition of slavery. 1784: Connecticut begins a gradual abolition of slavery, freeing future children of slaves, and later all slaves 1784: Rhode Island begins a gradual abolition of slavery. 1787: The United States in Congress Assembled passed the Northwest Ordinance of 1787 outlawing any new slavery in the Northwest Territories. 1799: New York State passes gradual emancipation act freeing future children of slaves, and all slaves in 1827. 1802: Ohio writes a state constitution that abolishes slavery. 1804: New Jersey begins a gradual abolition of slavery, freeing future children of slaves. Those born prior to the Act remain enslaved for life. 1805: Great Britain: bill for Abolition passed in Commons, rejected in the House of Lords. 1806: U.S. President Thomas Jefferson in a message to Congress calls for criminalizing the international slave trade, asking Congress to "withdraw the citizens of the United States from all further participation in those violations of human rights … which the morality, the reputation, and the best of our country have long been eager to proscribe." 1807, 2 March: Jefferson signs the Act Prohibiting Importation of Slaves into law in the U.S. which took effect 1 January 1808. 1807: In the U.S. Northwest Territory (present-day Michigan), 1808: In the United States, Act Prohibiting Importation of Slaves takes effect 1 Jan. .