New York Times investigative journalist Nikole Hannah-Jones spearheaded the 1619 Project, a landmark initiative unveiled this summer that marked the 400th anniversary of the arrival of the first enslaved Africans in Britain’s mainland North American colonies.

During a visit to Harvard this week, she made a surprising disclosure: While she had considering the project for years beforehand, its development was partly prompted by an exchange on Twitter.

“I got into an argument where someone said, ‘Slavery was a long time ago. Why don’t you get over it?’” she said Wednesday evening in a discussion with Henry Louis Gates Jr., director of the Hutchins Center for African & African American Research at Harvard. The talk drew a capacity crowd to the Smith Campus Center. “I realized we couldn’t get over it because America hasn’t gotten over it, and nobody wants to get over it more than black folks.”

This interaction, she said, led her to think about how slavery and its legacy have often been erased from the nation’s history. “Everyone in high school knows about the Mayflower, but nobody has been taught about the other ship, the White Lion,” she said, referring to the first English ship that brought enslaved Africans to the colonies in 1619. “I thought that an anniversary was approaching that most Americans would never hear of. Like most of black history, it would pass without most of us knowing.”

Originally published as a special issue of The New York Times Magazine on Aug. 14, the 1619 Project was later expanded in the paper and its website, and Hannah-Jones said that she is now working on a book version. Her talk with Gates focused on the evolution of the initiative. As she recalled, the magazine’s editor in chief, Jake Silverstein, proved receptive when she proposed that an entire issue of the magazine be devoted to the issue of slavery.

“I had been thinking about this and reading obsessively for 25 years about all the inequalities in American life that can be traced back to slavery. So I came in with an idea that they hadn’t heard before, and by then I had gathered enough trust that they knew I could deliver on what I promised.”

The idea also got a lift because of the timing, she said. It might not have had the same impact had it come during the Obama administration. “It was The Times, the paper of record, making the argument that the system of racial slavery was at the bedrock of our founding. And it appeared at a moment in time when people were thinking, ‘How the hell did we get here?’”