African-American slaves who worked 12-hour days, six days a week between 1793 and 1800 to help build the U.S. Capitol building, were honored this week with a pair of commemorative plaques that will be permanently displayed inside the Capitol building.

“This is a long overdue recognition of a sad and largely unknown chapter in our nation’s history,” said IAM Executive Assistant Diane Babineaux, who attended the ceremonial unveiling of the plaques.

The federal government rented the slaves from local slave owners at a rate of $5 per person per month. In addition to working on the building, slaves worked in quarries extracting the stone for the Capitol. Other slaves worked as carpenters, while others worked at sawing stone and timber.

“Just imagine, the United States government paying your owner, not you, but your owner $5 a month for your labor,” said Georgia Democratic Rep. John Lewis. “This Capitol, the most recognizable symbol of our democracy, was not built overnight, it was not built by machines. It was built through the backbreaking work of laborers and slave laborers."