WASHINGTON (AP).- 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 opened 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