A new memorial to early American slaves has refocused public attention on a dark chapter in American history and prompted a reassessment of its first president, George Washington.
The President's House, a partial reconstruction of the residence of Washington and his successor, John Adams, from 1790 to 1800, opened this week after a three-year excavation and restoration costing $11.2 million.
It commemorates the lives of nine African-descended slaves who had been kept there by Washington and highlights the stark contrast between their captivity and the beginnings of American democracy that emphasized individual liberty.
The memorial also aims to boost understanding of the horrors of slavery and draw attention to continuing racial divisions in America, said Philadelphia mayor Michael Nutter.
"We are a nation that lives with the as-yet unresolved issue of race," Nutter, who is black, told a largely African American audience at an opening ceremony.
He added that Washington operated a "devious scheme" to deny freedom to his slaves despite a Pennsylvania law that could have provided it.
"He did not choose to grant freedom to the people he held as slaves," Nutter said.
Michael Coard, a Philadelphia attorney who had pressed for the site to emphasise slavery rather than the early years of the US presidency, said the site shows that early America was built on the backs of slaves.
"I know I'm being named as the angriest black man in America," said Coard, whose Avenge the Ancestors Coalition led the campaign for the focus on slavery. "However, today, I'm ecstatic because history is being made."
Coard rejected critics' arguments that the site puts too much emphasis on slavery.
"Because slavery permeated the President's House, it must permeate this project," Coard said. "We have finally begun to avenge you," he said of the nine slaves whose names are etched into the walls of the house.
"We will never forget you," Coard added.
The house is just steps away from the Liberty Bell, which is one of the most famous emblems of the American Revolution. On July 8, 1776 it was used to summon Philadelphians to the first public reading of the Declaration of Independence.
Around the walls of the President's House information panels and video screens describe the lives of slaves, and include a timeline of the slave trade, stories of slave life on the site, and a quote from Washington saying: "The idea of freedom might be too great a temptation for them to resist."
The President's House is managed by the National Park Service and is open 365 days a year.