In her speech Monday night at the Democratic National Convention in Philadelphia, Michelle Obama said she wakes up "every morning in a house that was built by slaves." She spoke about the feeling of watching her daughters, "two beautiful, intelligent, black young women playing with their dogs on the White House lawn."

She spoke along similar lines in her commencement address at City College in New York this past June, describing the feeling of living "in a house that was built by slaves" and watching her daughters head off to school each day, "waving goodbye to their father, the president of the United States, the son of a man from Kenya who came here to America — to America for the same reasons as many of you: to get an education and improve his prospects in life."

At the commencement, Obama added that while the Founding Fathers probably couldn't have envisioned such a scene, City College's multinational, multilingual, multiracial graduating class represents the promise of America. "Their legacy is very much your legacy and your inheritance. And don't let anybody tell you differently. You are the living, breathing proof that the American dream endures in our time," Obama said.

In Selma, Ala., last year, on the 50th anniversary of the Bloody Sunday protest march, President Obama also referenced the White House's slave origins. He said America has been made by pioneers, immigrants, survivors, defectors, strivers and, also, "the slaves who built the White House and the economy of the South."

Clearly, the Obamas feel it is important to use their platform to remind the public, repeatedly, of these facts. Of course, not everyone is enthralled, or even convinced that all of this history is real, much less crucial. As Julie Hirschfeld Davis pointed out in the New York Timesabout Monday night's speech at the convention, "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 on racial lines."

But others say it's important for the Obamas to speak forthrightly on issues of race in the United States. At NBC News, Adam Howard wrote about why Michelle Obama's speech matters. "In one of several subtle nods to America's uncomfortable and ongoing navigation of race matters, Michelle Obama acknowledged the toll that ugly rhetoric directed at her husband's heritage has had on her children. And she managed to spin even that harsh reality in a positive light, highlighting her family's resilience in the face of hate," Howard wrote.

Howard also pointed out that a black family living in a house built by slaves is an irony that Michelle Obama is uniquely equipped to address, and one that someone like Hillary Clinton will never be able to talk about in quite the same way.

As many are reflecting on this week, we're wrapping up eight years in which a black family has occupied the White House. There are third-graders who have never known anything else. And in an election year where the roster of serious presidential hopefuls has included women, a Jewish man, two Latinos and an Indian-American, it can be easy to forget where we're coming from — that in our nation's 240-year history, we had never had a president who was not white until Barack Obama, and we've never had one who wasn't a Christian male. It's easy to forget that we are still very much living in an era of firsts — or pre-firsts, as the case may be.

It remains easy to forget, or ignore, or even deny, that the number of black Americans to hold office in the White House will almost certainly never come close to the number of black slaves once forced to toil there.

But with the world watching, Michelle Obama asked us once again to remember that legacy.

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