Thomas Jefferson wrote "all men are created equal" to declare U.S. independence from Britain, yet he was also a lifelong slave owner who freed only nine of his more than 600 slaves during his lifetime.

That contradiction between ideals and reality is at the center of a new exhibit opening Friday as the Smithsonian Institution continues developing a national black history museum. It offers a look at Jefferson's Monticello plantation in Virginia through the lives of six slave families and artifacts unearthed from where they lived.

The exhibit, "Slavery at Jefferson's Monticello: Paradox of Liberty," was developed with Monticello and will be on view at the National Museum of American History through mid-October. It includes a look at the family of Sally Hemings, a slave. Most historians now believe she had an intimate relationship with the third president and that he fathered her children.

Museum Director Lonnie Bunch said his staff can test ideas by building exhibits before the National Museum of African American History and Culture is finished.

It will be the first museum added to the National Mall since 2004. A groundbreaking is planned for Feb. 22, and it's scheduled to open in 2015 near the Washington Monument.

Bunch said museum officials want to see how the public responds to subjects, such as slavery, as they try to present history for the widest possible audience.

Slavery, he said, is still the "last great unmentionable" in public discourse but central in shaping American history.

"This is a story we know we have to tell, and this is a story we know is going to be difficult and going to be challenging, but this new museum has to tell the story," he told The Associated Press. "In many ways, the Smithsonian is the great legitimizer, so if we can wrestle with slavery and Jefferson, other people can."

A portion of the exhibit devoted to the Hemings-Jefferson story marks the first time the subject has been presented on the National Mall.

Curators stopped short of making a definitive statement in the exhibit about the relationship, but they wrote that it was likely an intimate one, based on documentary and genetic evidence.

"On the one hand it's not a breakthrough for scholars. We've known this for a long time," Bunch said. "I think that the public is still trying to understand it."

Many artifacts, including tools and kitchen ceramics, are on public view for the first time, exploring the work and lives of slave families who lived on Jefferson's plantation. Among the pieces on display is a hand-crafted chair built by John Hemings, Sally Hemings' brother, to replicate a set of French chairs at Monticello.

While such items may have been seen by 450,000 people a year at Monticello, they are accessible to millions of visitors at the Smithsonian, curators said.

In the exhibit, oral histories from descendants of Jefferson's slaves reveal stories passed down through families for generations, along with detailed records kept by Jefferson.

For example, Jefferson bought George and Ursula Granger and their sons as slaves in 1773, and Ursula became a "favorite housewoman" of his wife. Jefferson eventually made George Granger the overseer of Monticello, the only slave to rise to that position and receive an annual wage.

Later, the first baby born in the White House was the son of Wormley and Ursula Hughes, who belonged to Jefferson.

"We can begin to understand slavery, not as an abstraction but through the stories of individuals and families who were surviving within a system that denied their humanity," said Leslie Green Bowman, president of the Thomas Jefferson Foundation that runs Monticello.

A related website will showcase the "Getting Word" oral history project.

Curators also explore the importance of slavery in early U.S. history and Jefferson's views on enslavement, which he called an "abominable crime."

The small laptop portable desk he used to draft the Declaration of Independence is placed front and center in the exhibit, borrowed from the Smithsonian's permanent presidential gallery.

Shannon Lanier, 32, of New York City, a ninth generation descendant of Jefferson and Hemings through their son Madison Hemings, said he has known about his ancestors for years from stories told by his mother and grandmother.

Having such an exhibit at the Smithsonian is a breakthrough, he said, because it's past time for more people to know about Jefferson's history with slavery.

"This is a great catalyst for conversation," he said, standing near a bronze statue of Jefferson. "It's really hard for people to understand slavery and Thomas Jefferson. He was a president, why couldn't he set them free?"

"This helps enlighten people about ... how complex it was."

Bill Webb of New York City learned only in 2006 that his ancestor Brown Colbert was a slave connected to Monticello as the grandson of Elizabeth Hemings, Sally Hemings' mother _ a discovery he called "mind blowing."

"On any research that you do, I think it's exciting. But with slavery, it's certainly disturbing sometimes," he said. "But it's fact. It's good to know from whence one comes."

As for Jefferson, Webb said he was "a product of his time."

Until the mid-1980s, Monticello avoided the difficult topic of slavery. But decades of research and archaeology at the site, along with an oral history project begun in 1993 with descendants of slaves, helped piece together a fuller picture of slave life, said Monticello Curator Elizabeth Chew.

"Twenty years ago, we could not have done this show," she said.

Smithsonian Curator Rex Ellis said understanding Jefferson's place in history requires a deeper understanding of his entanglement with 607 enslaved men, women and children.

"We have to give voice to them," Ellis said. "They represent the community who brought him to his father on a pillow when he was born to those who adjusted the pillow under his head when he died."

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National Museum of African American History and Culture: http://nmaahc.si.edu/

Monticello: http://www.monticello.org/

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Brett Zongker can be reached at https://twitter.com//DCArtBeat