First lady Michelle Obama talks with students before they performed Civil War-era scenes at Decatur House on Wednesday. (Susan Walsh/AP)

Michelle Obama stepped onto the second floor of the historic Decatur House in downtown Washington. Accompanied by her usual entourage of aides and Secret Service agents, the first lady walked around what had been the house’s slave quarters, its original wooden beams exposed to reveal a rectangular structure once divided into four tight rooms that housed as many as 20 men and women.

In one of those rooms once lived Charlotte Dupuy, an enslaved woman whose life couldn’t have been more different from Obama’s. The intersection of the first descendant of slaves to serve as first lady with Dupuy, who created a stir of her own in political Washington, was brief but profound. And it occurred in a space that represents the last trace of people enslaved within sight of the White House.

Obama recalled the slaves “who spent their lives within shouting distance of one of the most powerful buildings on the planet — a bastion of freedom and justice for all,” noting that their “stories are a part of so many of our families’ histories, including my own.”

As Obama was ushered through the slave quarters, accompanied by a historian, there was no mention of Dupuy (pronounced “doo-pwee”) — although she may have been the most famous enslaved woman to ever reside in the slave quarters at Decatur House.

Like Obama, Dupuy was a wife and mother of two. She lived in the quarters in the late 1820s, when her owner, Secretary of State Henry Clay, rented the large brick residence on Lafayette Square. She worked in the home, tending to the needs of Clay’s wife, Lucretia. Dupuy’s husband, Aaron, was Clay’s manservant.

By 1829, Clay’s political party had been turned out of office and he prepared to return home to Kentucky. Dupuy, who was about 42, refused to go. Born in Cambridge, Md., she enlisted a lawyer to file a court case suing Clay for her freedom on the grounds that her mother had been freed and Dupuy had been promised freedom by her previous owner. As her case worked its way through the courts, she stayed at Decatur House as a paid employee of the next secretary of state and future president, Martin Van Buren.

Newspapers covered her lawsuit, which caused a scandal for the politician, who hoped to someday run for president. Clay was angry, said biographer Jeanne Heidler, co-author of “Henry Clay: The Essential American.” He thought of himself as a benevolent slave owner and believed that abolitionists had prompted Dupuy to file the suit to embarrass him. He instructed his lawyer to fight Dupuy’s claim. When she lost in court, Clay allowed Dupuy to be held in jail in Alexandria and then had her taken south. He eventually freed her — 11 years later.

Dupuy’s story, key to the history of Decatur House, was not mentioned, but Obama seemed to evoke it in remarks made as part of the announcement Wednesday of a $1 million grant from American Express to the White House Historical Association to preserve the house and slave quarters. The Decatur House is owned by the National Trust for Historic Preservation and managed by the historical association.

Obama said the slaves held onto a quiet hope and prayer “that they too, and perhaps their children, would someday be free.”

“These stories of toil and sweat and quiet, unrelenting dignity” are “vital to our national memory,” she said.

The visit to the slave quarters was not Obama’s first encounter with the slave trade that shaped so much of America’s history. On a trip to Ghana in July 2009, the first family walked through the Cape Coast Castle, one of a number of slave castles that were part of the trading of Africans into bondage. Obama also has acknowledged that the White House, which has become such an important part of her family’s story, was built in part with slave labor.

As she looked around the space in which Dupuy and other slaves lived, Obama was joined by American Express chief executive Kenneth Chenault, one of the few African Americans to serve as CEO of a Fortune 500 company. They saw the ways the Decatur House and slave quarters are used to teach schoolchildren about the history of the presidential neighborhood. A group of sixth-graders from Willow Springs Elementary School in Fairfax giddily greeted Obama and, as part of their interactive learning, acted out the signing of the Emancipation Proclamation and other Civil War-era scenes in period clothing. Obama sat, applauding them.

After the tour and student performance, Obama and her motorcade made the short but monumental trip from the slave quarters to the White House.