Ketanji Brown Jackson has been sworn in to the US Supreme Court, shattering a glass ceiling as the first black woman on the nation’s highest court.
The 51-year-old, who is the court’s 116th justice, took the place of the justice she once worked for.
Justice Stephen Breyer’s retirement took effect at noon on Thursday.
Moments later, joined by her family, Ms Jackson recited the two oaths required of Supreme Court justices, one administered by Mr Breyer and the other by chief justice John Roberts.
“I am truly grateful to be part of the promise of our great nation. I extend my sincerest thanks to all of my new colleagues for their warm and gracious welcome.”
Chief justice Roberts welcomed Ms Jackson “to the court and our common calling”.
The ceremony was streamed live on the court’s website.
Ms Jackson, a federal judge since 2013, is joining three other women, Justices Sonia Sotomayor, Elena Kagan and Amy Coney Barrett – the first time four women will serve together on the nine-member court.
Mr Breyer’s earlier-than-usual announcement and the condition he attached was a recognition of the Democrats’ tenuous hold on the Senate in an era of hyper-partisanship, especially surrounding federal judgeships.
The Senate confirmed Ms Jackson’s nomination in early April, by a 53-47 mostly party-line vote that included support from three Republicans.
Ms Jackson had been in a sort of judicial limbo since then, remaining a judge on the federal appeals court in Washington, DC, but not hearing any cases.
Mr Biden elevated her to that court from the district judgeship to which she was appointed by former president Barack Obama.
That will give her time to settle in and familiarise herself with the roughly two dozen cases the court already has agreed to hear starting in October as well as hundreds of appeals that will pile up over the summer.
The court issued final opinions earlier on Thursday after a momentous and rancorous term that included overturning Roe v Wade’s guarantee of the right to an abortion.
One of Thursday’s decisions limited how the Environmental Protection Agency can use the nation’s main anti-air pollution law to reduce carbon dioxide emissions from power plants, a blow to the fight against climate change.