President Biden on Monday formally designated the former site of a notorious boarding school for Native American children as a national monument, issuing a formal apology for the practice of forcibly removing children to such schools.

Introducing Biden at the White House Tribal Nations Summit, Interior Secretary Deb Haaland, the first Senate-confirmed Native American Cabinet secretary, described Biden as “the best president for Indian Country in my lifetime,” crediting the administration’s work on tribal funding and missing and murdered Indigenous women (MMIW). Haaland presented the president with a tribal blanket as attendees chanted, “thank you, Joe.”

Biden formally declared the monument at the Pennsylvania site of the Carlisle Indian Industrial School, which was established in 1879 as the first such school outside a Native American reservation. Over the next four decades, more than 7,800 children were forced to attend the schools, where their hair was cut and they were forbidden to speak Indigenous languages or wear traditional clothing. Richard Henry Pratt, the school’s founder, notoriously described its mission as “kill the Indian, save the man.”

Rough counts estimate nearly 1,000 children died in the care of the so-called industrial schools, with the actual number likely higher.

In his remarks, Biden called the use of such schools “a dark chapter that spanned 150 years … in which entire generations of Native children were literally stolen from their family members and tribes and sent away to boarding schools.”

“We don’t erase history, we acknowledge it and we learn from it so we never repeat it again,” the president added. “We remember so we can heal, that’s the purpose of memory.”

The president announced the administration will develop a “10-year plan to revitalize Native languages” as part of efforts to redress the cultural knowledge lost as a result of schools like Carlisle. The 24.5-acre Carlisle, Pa., monument will be jointly managed by the Department of the Army and the National Park Service.