http://en.wikipedia.org/wiki/Quock_WalkerThrough 94% of the 698,00o slaves in the United States were below the Mason-Dixon Line by 1790:
http://www.slavenorth.com/emancipation.htmOne side note, Vermont often claims to have abolished slavery in 1777, when it declared itself independent (Vermont was NOT so recognized by the United States nor any other country). Vermont became a State in the United States in 1791 AFTER the US Constitution had been adopted.
Anyway, the wording of Vermont's Abolish of slavery is more that no one could be made a slave as opposed to any affect on someone who was a slave AND records exists of Slaves in Vermont while after 1800. Given the stresses of the Revolution it became hard to keep blacks as slaves, thus most northern slaves won their freedom during the Revolution by either joining the British or taking up arms for the United States itself. Thus slavery was for all practical purposes abolished by the Revolution north of the Mason-Dixon Line by 1783, through legally slavery existed in northern states for decades afterward (New Jersey had a handful of slaves till the adoption of the Post Civil War Amendment abolishing slavery).
More on Vermont and Slavery:
http://www.timesargus.com/article/20090201/FEATURES07/902010318http://www.slavenorth.com/vermont.htmPlease note just because a country outlaws slavery does NOT mean slavery disappears from that nation. The best example of this is Mexico. Mexico Abolished slavery in its 1821 Constitution but even as late as the US Civil War it was still a practice to sell Native Americans as slaves in Mexico (Brigadier General Kit Carson suggested this to his superior in 1864 after the Navajo war, his superior told him no given the Emancipation Proclamation of two years before, but it is noted for the fact such selling of Native Americans as Slaves were still common practice in the 1860s in the US Southwest and Northern Mexico, over 40 years after slavery was "abolished" in Mexico).
Pennsylvania outlaws slavery in 1780, but any one born a slave (or to a slave) would stay a slave till they turn 28 (Given the term in the act "to a slave", Slavery was "Legal" till 1848 in Pennsylvania, but there is no record of such a situation actually occurring):
http://www.slavenorth.com/pennsylvania.htmin 1784 Connecticut abolishes slavery (Gradual emancipation at least 54 slaves as late as 1840)
http://www.slavenorth.com/connecticut.htmin 1784 Rhode Island abolishes slavery (Gradual emancipation at least five slaves as late as 1840)
http://www.slavenorth.com/rhodeisland.htmIn 1799 New York State passes gradual emancipation act
In 1804 New Jersey abolishes slavery (Through please note the above on slaves in New Jersey till 1866)
http://en.wikipedia.org/wiki/Abolition_of_slavery_timelineThe rest of the Northern states, Ohio westward never had slavery under the terms of the Northwest ordinance of 1783:
http://en.wikipedia.org/wiki/Northwest_OrdinanceNo Southern State Abolished Slavery till the adoption of the Federal Constitutional Amendment abolishing slavery and "involuntary servitude" in 1866 (Through the Southern Congress did pass a bill freeing any slave who volunteer to serve in the Southern Army, but that was in January 1865, to late for any affect during the Civil War).
More on Modern Slavery:
http://www.anti-slaverysociety.addr.com/index.htmhttp://www.anti-slaverysociety.addr.com/toc.htmNo