President Biden ventured into Native American territory on Friday to offer a formal apology on behalf of the U.S. government for the mistreatment of generations of children who were taken away from their families in an effort to strip them of their culture, history and language.

During a visit to the Gila River Indian Community in Arizona, Mr. Biden decried what he called “a sin on our soul” and promised to do more to make up for the federal government’s former policy of forcibly removing Native American children and putting them in boarding schools where they faced abuse and neglect that led in some cases to death.

“The federal government has never, never formally apologized for what happened — until today,” the president told a cheering crowd that included families afflicted by the policy. “I formally apologize as president of the United States of America for what we did. I formally apologize. It’s long overdue.”

He added that “quite frankly, there’s no excuse that this apology took 50 years to make” and acknowledged that it could only mean so much after so long. “I know no apology can or will make up for what was lost during the darkness of the federal boarding school policy,” Mr. Biden said. “But today, we’re finally moving forward into the light.”

Mr. Biden’s visit culminated years of study and discussion by his administration led by Deb Haaland, the nation’s first Native American interior secretary, whose own family was affected by a practice that lasted from the early 1800s to the late 1960s. An investigative report by her department in July found that at least 19,000 Native children were sent to federal boarding schools, and nearly 1,000 died while attending them.

In addition to an apology, the report called on the federal government to create a national memorial to commemorate the children’s deaths and educate the public; invest in research and help Native communities heal from intergenerational stress and trauma; and revitalize Native languages.