Any discussion about the history of slavery in the United States usually conjures up images of the antebellum South with slaves laboring on cotton plantations. But as a new exhibition entitled "Slavery in New York City" reveals, the Northern States, and in particular New York, participated in and profited from the slave trade.

The New York Historical Society's exhibition gives voice to a segment of the population that history once tried to forget, the slaves who helped build New York City. The horrors of enslaving human beings are heard in one of the show's audio reenactments.

NARRATOR:  "I seen him strip Betty naked and make her stand in the freezing yard from nigh on an hour. At other times he ordered her to hold out her hand and poured boiling water over it. And he was saying, 'Am I not a good doctor to my Negroes?'"

First under Dutch, and later English rule, slaves provided almost 40 percent of New York City's workforce, constructing Broadway, the original City Hall and the wall that gave its name to Wall Street. During the United States' War of Independence, patriots used anti-slavery rhetoric in their fight to break free from Britain, even as Revolutionary leaders themselves owned slaves. George Washington, arguably the country's foremost symbol of liberty, warned that if Americans didn't resist the British, they risked becoming, as he put it, "as tame and abject slaves as the blacks we rule with such arbitrary sway." 

Leslie Harris, a professor at Emory University in Atlanta, Georgia, wrote the companion book to the exhibit. At the show's opening she explained that New York had more slaves than any of the original 13 colonies.

"Forty-one percent of New Yorkers owned slaves during the colonial era," she noted.  "And that is more than the 25 percent of households in the South that owned slaves. And if 41 percent of New Yorkers owned slaves, you can bet the other 59 percent wished that they did. Slavery was the path to creating wealth in New York and in much of the nation."

And yet much of the world believes that slavery was primarily a Southern institution in the United States, a myth, according to Professor Harris, that the North perpetuated.

"When the North went south to fight for union and ultimately to end slavery, the reigning story became of a free North ending one of the great evils," she added.  "And when you're creating a story like that it's very hard to say, 'Oh by the way we were slave owners, too.'"

Founded 201 years ago by a slave owner, The New York Historical Society provides plenty of evidence of the city's active slave trade: bills of sales, advertisements to find runaways and the ledger from a ship noting how the crew traded guns, cloth and ivory in exchange for 124 human beings. The son of the ship's owner signed the Declaration of Independence representing New York. But, says curator Richard Rabinowitz, any sign of moral doubt about human trafficking is missing from the show's hundreds of documents.

"When you see the bill of sales for Violet, a 15-year-old girl, this one is on a printed form the way we sign lease agreements in New York city today, I wanted you to have that shudder that I felt, you know that the transaction of a human being can also be done on a printed form," he said.  "One of the great shocks is we don't find diaries and letters and sermons by New Yorkers debating the question of the morality of slavery, at least until the 1770s."

During the early 1800s, however, New York City became a center of the movement to abolish slavery, and by 1827 legally prohibited the practice. While some critics have suggested that focusing on this shameful blight on the city's past could generate volatile reactions, Professor Harris disagrees.

"We underestimate the good feeling that's generated when people see that their history is being acknowledged fully for one of the first times publicly," said Ms. Harris.  "That's actually a community building moment when black and white New Yorkers can walk through these galleries together and have a dialogue that's fruitful, have a conversation in a good way."

The ambitions for this show are large. School textbooks do not often discuss the Northern slave trade so the organizers of Slavery in New York included extensive outreach programs for children in the belief that through understanding our past we can better understand and shape our present.