Four hundred years have passed since the arrival of the first 20 slaves into the US.

Many of the United States' most famous buildings were built by enslaved African Americans, including the White House and the US Capitol.

Here are 15 famous American landmarks you may not have known were built by slaves.

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In 2016, former first lady Michelle Obama declared as a sign of how far the nation has come: "I wake up every morning in a house that was built by slaves."

She was talking about the White House. And as the first African American first lady speaking to the Democratic National Convention, she struck a chord. Some fact checkers and political pundits may have raced to their history books, ready to dispute the claim. But she was right.

Obama could have been talking about the US Capitol, or Trinity Church in New York, or Georgetown University in Washington. Slaves built some of the United States' most symbolic buildings.

This month marks 400 years since the arrival of the first 20 slaves into the US. Earlier this week, Reuters published a photo-series called "Built by my family: America's grand buildings built by slaves." It's showcasing the issue, looking at some the most well-known landmark buildings built by slaves. Here are 15 of them.