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. In Illinois, for example, while the trade in slaves was prohibited, it was legal to bring slaves from Kentucky into Illinois and use them there, as long as the slaves left Illinois one day per year (they were "visiting"). 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. Agitation against slavery There was legal agitation against slavery in the Thirteen Colonies starting in 1752 by lawyer Benjamin Kent, whose cases were recorded by one of his understudies, the future president John Adams. Kent represented numerous slaves in their attempts to gain their freedom. He handled the case of a slave, Pompey, suing his master. In 1766, Kent was the first lawyer in the United States to win a case to free a slave, Jenny Slew. He also won a trial in the Old County Courthouse for a slave named (1771). Kent also handled Lucy Pernam's divorce and the freedom suits of Rose and Salem Orne. 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. This struggle took place amid strong support for slavery among white Southerners, who profited greatly from the system of enslaved labor. But slavery was entwined with the national economy; for instance, the banking, shipping, and manufacturing industries of New York City all had strong economic interests in slavery, as did similar industries in other major port cities in the North. The Northern textile mills in New York and New England processed Southern cotton and manufactured clothes to outfit slaves. By 1822, half of New York City's exports were related to cotton. Slaveholders began to refer to slavery as the "peculiar institution" to differentiate it from other examples of forced labor. They justified it as less cruel than the free labor of the North. The principal organized bodies to advocate abolition and anti-slavery reforms in the north were the Pennsylvania Abolition Society and the New York Manumission Society. Before the 1830s the antislavery groups called for gradual