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.