Fact-checking Michelle Obama’s critics: Slaves did help build the White House.

WASHINGTON — When Michelle Obama said in her prime-time televised address to the Democratic National Convention on Monday night that the White House had been built by slaves, she was citing a littlediscussed fact that dramatized her own African-American family’s place in history.

But the first lady’s assertion was met with derision and disbelief by some, who questioned whether it was true and said her choice to mention it amounted to an attempt to divide the country along racial lines.

There is little dispute among historians that slaves had a role in the building of the White House. According to the White House Historical Association’s website, planners had initially intended to import workers from Europe but had trouble recruiting any, so they “turned to African-American — enslaved and free — to provide the bulk of labor that built the White House, the United States Capitol, and other early government buildings.”

The association said slaves had worked at the government’s quarry in Aquia, Va., to cut the stone for the walls of the White House. The construction team included white laborers from Maryland and Virginia and immigrants from Ireland, Scotland and other parts of Europe, the association said.

Jesse Holland, a Washingtonbased journalist who wrote The Invisibles: The Untold Story of African American Slaves in the White House, said that most people never thought about how the president’s house and other important government buildings had been constructed, but that historians had long acknowledged the role of slaves.

“If you think about it, it would be pretty obvious: The White House is a neo-Classical mansion that was built in the South during slavery, and a majority of the mansions that were built in the South during slavery used slaves,” Holland said in an interview.

“We as Americans build up a myth of our country, and a lot of times, we don’t want to look behind that myth,” he added. “For me, finding out the truth and acknowledging the participation of everyone in the construction of this country just makes our country richer.”

Obama was reaching for a similar point Monday, emphasizing as President Barack Obama often does that the strengths of the United States spring in part from its ugly and painful past.

She said America’s story was “the story that has brought me to this stage tonight, the story of generations of people who felt the lash of bondage, the shame of servitude, the sting of segregation, but who kept on striving and hoping and doing what needed to be done so that today, I wake up every morning in a house that was built by slaves, and I watch my daughters — two beautiful, intelligent, black young women — playing with their dogs on the White House lawn.”

It was not the first time the she has used the line — it also appeared in a commencement address she delivered in June at the City College of New York. It got more attention Monday night, when Obama delivered a speech viewed by many more Americans amid an ever-more-intense presidential campaign.

The comment was met with derision by many conservatives on social media, some of whom argued it was false because the White House had been built with the assistance of white people and had since been renovated. The right-leaning news website Infowars called it “race baiting.”

The assertion also sparked swift fact-checking by the news media (PolitiFact rated it “true”), which some observers suggested was its own form of racially tinged disrespect.

“PolitiFact Schools White People Who Refused to Believe White House Was Built by Slaves,” said a headline on The Root, an African-American news and culture website.

Barack Obama has referred to the role of slaves in building the White House; he spoke of it in March 2015 at a speech in Selma, Ala., to commemorate the 50th anniversary of “Bloody Sunday,” when state troopers attacked hundreds of people protesting peacefully for voting rights for African-Americans.

Michelle Obama mentioned it last month during a commencement address she delivered at the City College of New York, drawing backlash from conservative commentators, who called it unpatriotic.