In the mid- to late 1760s, 1,500 blacks lived in slavery in Philadelphia. Statewide, there were an estimated 5,600. The number of slaves peaked in the early 1780s at 6,855, according to historian Gary B. Nash.
Among the people who owned slaves in Philadelphia were Benjamin Franklin, Benjamin Chew, John Dickinson, Thomas Cadwalader, Samuel McCall, Samuel Mifflin, Robert Morris and Edmund Physick. They are some of the most prominent ones, whose names recur in accounts of the colonial city and for whom streets and counties and institutions are named. Many of Philadelphia's slaveholders were tradesmen - barbers, brewers, sailmakers, leather workers. According to Nash, "about one-quarter of the households in the city were involved in slavekeeping in the closing years of the 1760s."
By 1790, the number for the state had fallen to 3,760. And by 1810, to 795.
"Of the states south of New England, slavery died first in Pennsylvania and it died there the fastest," write Nash and Jean Soderlund in the 1991 book, Freedom by Degrees: Emancipation in Pennsylvania and Its Aftermath.
The motivations were complicated, the authors say. Quakers had been debating the morality of slavery for a century, and the first recorded North American protest against slavery was signed by a group of Quakers in Germantown in 1688 and sent, to no immediate effect, to other Quaker groups. But moral outrage was only one factor in slavery's demise in Pennsylvania, and not always the overriding one. Economics, politics and a propensity for slaves to free themselves had a lot to do with it.
Slavery withered more rapidly in Philadelphia than in surrounding areas, in part because slaves did not live as long, nor have as many children, as they did on farms. In 1810, 94 percent of the slaves in Pennsylvania were in seven rural counties.
Slavery was even more common in neighboring states. In 1790, Delaware had 8,887 slaves, New Jersey had 11,423, and New York 21,193.
In 1779, Pennsylvania passed the first abolition law in America. The measure was praised for embodying the spirit of enlightenment at the time, but its gradual terms were no godsend.
The law did not emancipate a single slave - anyone who was a slave the last day before it went into effect March 1, 1780, remained a slave until death unless freed by his or her owner. All children born of slaves after the law took effect could be kept enslaved until age 28. So it would have been possible for a slave girl, born on the last day of February 1780, to live out her life in slavery. And for her children, theoretically born as late as 1820, to remain slaves until 1848.
Total abolition didn't come to Pennsylvania until 1847.