The U.S. Constitution was written at a convention that met in Philadelphia from May 25 until September 17, 1787. At the time, slavery was legal and a vibrant economic institution in eight states, while two (Massachusetts and New Hampshire) had abolished it, and three others (Pennsylvania, Rhode Island, and Connecticut) had passed gradual abolition acts. There were about 700,000 slaves in the nation, with more than 600,000 in Virginia, South Carolina, North Carolina, and Maryland. Virginia’s 300,000 slaves constituted just over 40 percent of the state, while South Carolina’s 107,000 slaves made up 43 percent of the state. Slaves were property and enormously valuable. They were also central to the southern economy. Indeed, with the exception of real estate, slaves represented the single most valuable form of privately held property in the nation.