Meanwhile, Lumpkin sent two of his mixed-race daughters to finishing school in Massachusetts. According to Charles Henry Corey, a former Union army chaplain, Lumpkin later sent the girls and their mother to live in the free state of Pennsylvania, concerned that a "financial contingency might arise when these, his own beautiful daughters, might be sold into slavery to pay his debts."
"He was both an evil man and a family man," Schwarz says.
Lumpkin was in Richmond in April 1865 when the city fell to Union soldiers. Shackling some 50 enslaved and weeping men, women and children together, the trader tried to board a train heading south, but there was no room. He died not long after the war ended. In his will, Lumpkin described Mary only as a person "who resides with me." Nonetheless he left her all his real estate.
In 1867, a Baptist minister named Nathaniel Colver was looking for a space for the black seminary he hoped to start. After a day of prayer, he set out into the city's streets, where he met Mary in a group of "colored people," recalling her as a "large, fair-faced freedwoman, nearly white, who said that she had a place which she thought I could have." After the bars were torn out of the windows, Mary leased Lumpkin's jail as the site of the school that became Virginia Union University, now on Lombardy Street in Richmond.
"The old slave pen was no longer 'the devil's half acre' but God's half acre," Simmons wrote.
Mary Lumpkin went on to run a restaurant in Louisiana with one of her daughters. She died in New Richmond, Ohio, in 1905 at 72.
McQuinn, who is also a minister, hopes the site will one day become a museum. Though it has been reburied for the time being, she says it will never again be forgotten: "The sweetest part," she says, "is now we have a story to tell."
Abigail Tucker is Smithsonian's staff writer.