this period. In the antebellum period many slaves escaped to freedom in the North and in Canada by running away, assisted by the Underground Railroad, staffed by former slaves and by abolitionist sympathizers. Census enumeration found a total of 488,070 "free colored" persons in the United States in 1860. Abolitionism Most organized political and social movements to end slavery did not begin until the mid-18th century. The sentiments of the American Revolution and the equality evoked by the Declaration of Independence rallied many black Americans toward the revolutionary cause and their own hopes of emancipation; both enslaved and free black men fought in the Revolution on both sides. In the North, slaves ran away from their owners in the confusion of war, while in the South, some slaves declared themselves free and abandoned their slave work to join the British. In the 1770s, blacks throughout New England began sending petitions to northern legislatures demanding freedom; by 1800, all of the northern states had abolished slavery or set measures in place to gradually reduce it. While free, blacks often had to struggle with reduced civil rights, such as restrictions on voting, as well as racism, segregation, or physical violence. Vermont abolished slavery in 1777, while it was still independent, and when it joined the United States as the 14th state in 1791 it was the first state to have done so. All the other Northern states abolished slavery between 1780 and 1804, leaving the slave states of the South as defenders of the "peculiar institution". Massachusetts abolished slavery in 1780, and several other Northern states adopted gradual emancipation. In 1804, New Jersey became the last original Northern state to embark on gradual emancipation. Slavery was proscribed in the federal Northwest Territory under the Northwest Ordinance of 1787, passed just before the U.S. Constitution was ratified. The free black population increased from 8% to 13.5% from 1790 to 1810; most of whom lived in the Mid-Atlantic States, New England, and the Upper South, where most of the slave population lived at the time. The rights of free blacks fluctuated and waned with the gradual rise in power among poor white men during the late 1820s and early 1830s. The National Negro Convention movement began in 1830, with black men holding regular meetings to discuss the future of the black "race" in America; some women such as Maria Stewart and Sojourner Truth made