In colonial-era North America, the Society of Friends, otherwise known as the Quakers, stood almost alone in professing that slaveholding was incompatible with Christian piety. The Age of Enlightenment and the American Revolution, however, led more Americans to equate the slaves� right to freedom with the colonists� demand for independence. Consequently, Northern states began the gradual emancipation of their slaves. Although the federal government prohibited slavery in the Northwest Territory in 1787 and banned the trans-Atlantic slave trade in 1808, antislavery agitation dropped off due to the increasing profitability of Southern slavery. Most remaining, antislavery sentiment became channeled through the African Colonization Society, a group founded in 1816 to return blacks to their home continent.