WASHINGTON (AP) — President Biden on Friday will nominate to the Supreme Court a federal appeals court judge, Ketanji Brown Jackson, according to a person familiar with the matter. She would be the first Black woman selected to serve on a court that once declared her race unworthy of citizenship and endorsed segregation. 

In Judge Jackson, Mr. Biden delivers on a campaign promise to make the historic appointment and to further diversify a court that was made up entirely of white men for almost two centuries. He has chosen an attorney who would be the high court’s first former public defender, though she also possesses the elite legal background of other justices.

Judge Jackson would be the current court’s second Black justice — Justice Clarence Thomas, a conservative, is the other — and just the third in history.

The news was confirmed by a person familiar with the matter who spoke on the condition of anonymity to discuss it before the president’s official announcement later Friday.

She would also be only the sixth woman to serve on the court, and her confirmation would mean that for the first time four women would sit together on the nine-member court. 

The current court includes three women, one of whom is the court’s first Latina, Justice Sonia Sotomayor. 

Judge Jackson would join the liberal minority of a conservative-dominated court that is weighing cutbacks to abortion rights and will be considering ending affirmative action in college admissions and restricting voting rights efforts to increase minority representation.

Mr. Biden is filling the seat that will be vacated by Justice Stephen Breyer, 83, who is retiring at the end of the term this summer. 

Judge Jackson, 51, once worked as one of Justice Breyer’s law clerks early in her legal career. She attended Harvard as an undergraduate and for law school, and served on the U.S. Sentencing Commission, the agency that develops federal sentencing policy, before becoming a federal judge in 2013.

Her nomination is subject to confirmation by the Senate, where Democrats hold the majority by a razor-thin 50-50 margin with Vice President Harris as the tie-breaker. Party leaders have promised swift but deliberate consideration of the president’s nominee.

The next justice will replace one of the more liberal justices, so she would not tip the balance of the court, which now leans 6-3 in favor of conservatives. 

The Senate Judiciary Committee chairman, Dick Durbin, has said that he wants the Senate to move quickly on the nomination, and senators have set a goal of confirmation by mid-April. But that timeline could be complicated by a number of things, including developments between Russia and Ukraine and the extended absence of Senator Lujan of New Mexico, a Democrat who suffered a stroke last month and is out for several weeks. Democrats would need Mr. Lujan’s vote to confirm Mr. Biden’s pick if no Republicans support her.

Once the nomination is sent to the Senate, it is up to the Senate Judiciary Committee to vet the nominee and hold confirmation hearings. After the committee approves a nomination, it goes to the Senate floor for a final vote. 

The entire process passes through several time-consuming steps, including meetings with individual senators. While Justice Amy Coney Barrett was confirmed just four weeks after she was nominated ahead of the 2020 election, the process usually takes several weeks longer than that.

Judge Jackson was on the president’s short list as a potential nominee even before Justice Breyer retired. Mr. Biden and his team spent weeks poring over her records, interviewing her friends and family and looking into her background.

Mr. Biden has said he was interested in selecting a nominee in the mold of Justice Breyer who could be a persuasive force with fellow justices. Although Justice Breyer’s votes tended to put him to the left of center on an increasingly conservative court, he frequently saw the gray in situations that colleagues were more likely to find black or white.

Judge Jackson serves on the U.S. Court of Appeals for the District of Columbia Circuit, a position that Mr. Biden elevated her to last year from her previous job as a federal trial court judge. Three current justices — Thomas, Brett Kavanaugh and John Roberts, the chief justice — previously served on the same court.

Judge Jackson was confirmed to that post on a 53-44 Senate vote, winning the backing of three Republicans: South Carolina’s Lindsey Graham, Maine’s Susan Collins, and Alaska’s Lisa Murkowski.

Bipartisanship is important to Mr. Biden, who has often said he was reaching for GOP support as he closed in on a nominee. Another GOP connection: Judge Jackson is related by marriage to a former House speaker, Paul Ryan of Wisconsin.

In one of Judge Jackson’s most high-profile decisions, as a trial court judge she ordered a former White House counsel, Don McGahn, to appear before Congress. That was a setback to President Trump’s efforts to keep his top aides from testifying. The case was appealed, and a deal was ultimately reached for Mr. McGahn’s testimony.

Another highly visible case that Judge Jackson oversaw involved the online conspiracy theory “pizzagate,” which revolved around false internet rumors about prominent Democrats harboring child sex slaves at a Washington pizza restaurant. A North Carolina man showed up at the restaurant with an assault rifle and a revolver. Judge Jackson called it “sheer luck” no one was injured and sentenced him to four years in prison.

Judge Jackson has a considerably shorter record as an appeals court judge. She was part of a three-judge panel that ruled in December against Mr. Trump’s effort to shield documents from the House committee investigating the January 6, 2021, insurrection at the U.S. Capitol.

Judge Jackson was born in Washington, D.C., and grew up in Miami. She has said that her parents, Johnny and Ellery Brown, chose her name to express their pride in her family’s African ancestry. They asked an aunt who was in the Peace Corps in Africa at the time to send a list of African girls’ names and they picked Ketanji Onyika, which they were told meant “lovely one.”

Judge Jackson traces her interest in the law to when she was in preschool and her father was in law school and they would sit together at the dining room table, she with coloring books and he with law books. Her father became an attorney for the county school board and her mother was a high school principal. She has a brother who is nine years younger who served in the Army, including in Iraq, and is now a lawyer.