As the color drained from the sky, a group gathered before the white-stoned basilica of St. Denis, where dozens of French kings are buried, to pay homage to their ancestors.

Not to King Louis XIII, who authorized the slave trade in 1642, or his son, the Sun King, who introduced slavery’s legal code, both of whose remains are buried inside the gothic building. They came for the victims, who are honored by a modest memorial outside.

“This is Jean-Pierre Calodat,” said Josée Grard, 81, running her fingers along the name written on the globe-shaped sculpture as tambour drums echoed around her. “He was freed four years before abolition. His wife, Marie Lette, must be nearby.”

There are just four memorials like this around France. Last autumn, the government announced it would do more: build a “National Memorial for the Victims of Slavery” in Trocadéro Gardens, the tourist destination that is an Instagram favorite because of its clear view of the Eiffel Tower.

But the monument, intended as a gesture of reconciliation in a country that has been loath to address the unsavory parts of its past, has itself become a source of division.

It will bear the names of some 224,000 people who were freed from slavery by France in 1848, made citizens and assigned a family name.

While some see it as a hopeful sign of progress, others have dismissed it as contradictory lip service. Specifically, they say, by listing the names of people who were freed, the memorial will again glorify France for abolishing slavery, not atone for holding some four million people in bondage over two centuries.

The group that has lobbied for the memorial for decades, which includes Parisians who grew up in Guadeloupe and Martinique, hopes it will offer something more intimate.

“This is not a memorial for political confrontation, but one to give people peace,” said Serge Romana, a doctor who was named the co-director of the memorial together with a government cabinet minister. “To have the state honor these people, is to not be ashamed.”

In a country where national history is so important that the president has a special memorial adviser, the history of slavery — and its lingering effects — remains largely taboo. The capital is crowded with historical statues and commemorative plaques, yet only a handful speak to the issue. Not one of Paris’s more than 130 museums is dedicated entirely to slavery, or to the history of colonialism.

President Emmanuel Macron promised to change that and “look our past in the face.” He has taken some steps, like officially establishing the Foundation for the Memory of Slavery in 2018 and paying tribute last year to the Haitian revolutionary leader Toussaint Louverture in the French prison where he died.

The acute sensitivity among French leaders underscores a contradiction at the root of the national identity: How can the country that heralds itself as revolutionary champion of universal human rights have enslaved millions of people at the same time?

“The challenge is to integrate in a communal story the complexities and contradictions of a society,” explained Jean-Marc Ayrault, a former prime minister who leads the Foundation for the Memory of Slavery. “Our objective isn’t to pit communities against one another or create a war of personal histories. It’s to construct a shared history.”

His foundation does that often by highlighting French fighters against slavery over those who profited from and maintained it.

The committee pushing for the memorial was born in protest of just that kind of national reframing. On the 150th anniversary of France’s abolition of slavery in 1998, the government announced national celebrations with the slogan: “All born in 1848.”

“We said no — our people were created in slavery,” said Emmanuel Gordien, 65, another doctor and former independence activist from Guadeloupe. “We didn’t want to erase history.”

Together with Mr. Romana and other Guadeloupean activists, he put out a call for a funeral march through the streets of Paris, to pay homage to ancestors who had been enslaved. Tens of thousands came.

Later, the group formed an association named for that protest — the Committee of the May 23, 1998 March — to search for that history. They spent years digging into various French archives.

Mr. Gordien grew up learning that his great-great-grandfather Bouirqui had been born in West Africa, sold into slavery and named George, and that his family owned a piece of land in Guadeloupe that had been part of the former slave plantation.

“That kind of knowledge had been lost because of shame,” Mr. Gordien said, “and also because of French assimilation.”

For most others, their personal connection to this history remained vague. Enslaved people in the French colonies were typically called by only a first name, which makes deep genealogical research very difficult.

But the group discovered that in the wake of abolition, the French government had ordered its administrators to assign each new citizen a family name, so the men at least could vote. The names, the directive said, could not be that of former masters, should be inspired by ancient history and the calendar, and should vary infinitely.

“If you had an officer interested in fruit, you’d have a fruit name. If he was into rocks, you’d get rock or sand,” said Mr. Gordien, whose ancestor was given the name of Roman emperors.

The names were recorded in registers, which often included telling personal details — the names of the enslaved person’s parents, the type of labor they did, their village or former plantation and where they were born.

Volunteers compiled more than 160,000 records from Guadeloupe and Martinique and put all the information into two books and a searchable online registry. Those names will be combined with others found by historians and activists in other former French colonies — now overseas departments — where slavery was enforced.

Since then, the group has hosted weekly genealogy and research sessions out of its small office in the 20th arrondissement of Paris, to help people trace their own family stories. In some cases, their searches have unearthed documents from before abolition — ancient notary acts for the sale of enslaved people, whom they’ve been able to verify were the ancient relatives of community members. Their research often elicits strong reactions.

“One woman fell to the ground, like she’d had a stroke. Another person left right away — she didn’t want to know,” said Ms. Grard, who, after finding her own ancestors, has spent years volunteering with the group to help others do the same. “It’s a huge shock.”

But for others, the research leads to a deeper understanding of their past, themselves and how they connect into the larger story of France. “This is my family,” said Ms. Grard, hanging a paper lantern on the memorial by her ancestors’ names. “They are part of me.”

The memorial will offer both respect to their ancestors and healing for their living descendants, the group’s members say.

“We need to be at peace with this history and our link to this history,” Mr. Romana said. “It’s a path forward.”

Names on memorials are important, said Sarah Gensburger, the president of the international memory studies association and a sociologist and historian at Sciences Po university in Paris.

“It gives families a place to mourn when they don’t have graves,” she said. “It’s also a way to write yourself into the full story.”

Critics, however, question the decision to honor just 224,000 people and not the millions who suffered under French slavery.

“They want to pay homage to people who were enslaved, but they are putting up the names of people liberated by the Republic,” said Myriam Cottias, director of the International Research Center on Slavery and Post-Slavery in Paris. “That’s why they were successful in getting this monument — it glorifies the Republic.”

Lilian Thuram, a former French soccer star and antiracism educator, supports the idea of a memorial, but not with names assigned by the same French state that had enslaved them.

“Why not mark in marble all the names of the former enslavers and the people who enriched themselves through slavery?” he said.