<P> Most northern states passed legislation for gradual abolition, first freeing children born to slave mothers (and requiring them to serve lengthy indentures to their mother's masters, often into their 20s as young adults). As a result of this gradualist approach, New York did not fully free its last ex-slaves until 1827, Rhode Island had seven slaves still listed in the 1840 census . Pennsylvania's last ex-slaves were freed in 1847, Connecticut's in 1848, and New Hampshire and New Jersey in 1865 . </P> <P> None of the Southern states abolished slavery, but it was common for individual slaveholders in the South to free numerous slaves, often citing revolutionary ideals, in their wills . Methodist, Quaker and Baptist preachers traveled in the South, appealing to slaveholders to manumit their slaves . By 1810, the number and proportion of free blacks in the population of the United States had risen dramatically . Most free blacks resided in the North, but even in the Upper South, the proportion of free blacks went from less than one percent of all blacks to more than 10 percent, even as the total number of slaves was increasing through importation . </P> <P> Through the Northwest Ordinance of 1787 under the Congress of the Confederation, slavery was prohibited in the territories northwest of the Ohio River; existing slaves were not freed for years, although they could no longer be sold . This was a compromise . Thomas Jefferson proposed in 1784 to end slavery in all the territories, but his bill lost in the Congress by one vote . The territories south of the Ohio River (and Missouri) had authorized slavery . Northerners predominated in the westward movement into the Midwestern territory after the American Revolution; as the states were organized, they voted to prohibit slavery in their constitutions when they achieved statehood: Ohio in 1803, Indiana in 1816, and Illinois in 1818 . What developed was a Northern block of free states united into one contiguous geographic area that generally shared an anti-slavery culture . The exceptions were the areas along the Ohio River settled by Southerners, the southern portions of states such as Indiana, Ohio and Illinois . Residents of those areas generally shared in Southern culture and attitudes . In addition, these areas were devoted to agriculture longer than the industrializing northern parts of these states, and some farmers used slave labor . The emancipation of slaves in the North led to the growth in the population of northern free blacks, from several hundred in the 1770s to nearly 50,000 by 1810 . </P> <P> Throughout the first half of the 19th century, abolitionism, a movement to end slavery, grew in strength; most abolitionist societies and supporters were in the North . They worked to raise awareness about the evils of slavery, and to build support for abolition . </P>

When did the northern states became free states