Ketanji Brown Jackson marked a milestone in American representation on Thursday when she was sworn in as the first Black woman in history to sit on the nation's highest court -- officially taking on the title of justice.
Chief Justice John Roberts, in a brief ceremony at the Supreme Court, administered the constitutional oath to Jackson, and retiring Justice Stephen Breyer, who Jackson clerked for some 20 years ago, administered the judicial oath.
Her husband, Dr. Patrick Jackson, held two Bibles -- a family Bible and the Harlan Bible, a King James Bible donated to the Supreme Court in 1906 -- as Jackson smiled broadly and finished repeating the oaths.
"On behalf of all the members of the court, I'm pleased to welcome Justice Jackson to the court and to our common calling," Roberts said as the other seven other sitting justices attending applauded while Jackson beamed.
Breyer shook her hand and whispered, "Congrats," before patting her on the back.
"With a full heart, I accept the solemn responsibility of supporting and defending the Constitution of the United States and administering justice without fear or favor, so help me God," Jackson said in a written statement. "I am truly grateful to be part of the promise of our great Nation."
She thanked her new colleagues "for their warm and gracious welcome," and said she is "especially grateful for the time and attention given to me by the Chief Justice and by Justice Breyer."
"Justice Breyer has been a personal friend and mentor of mine for the past two decades, in addition to being part of today's official act," she wrote. "In the wake of his exemplary service, with the support of my family and friends, and ever mindful of the duty to promote the Rule of Law, I am well-positioned to serve the American people."
Breyer, in his own statement, said he's "glad today" -- for "Ketanji," "for my fellow Justices," and "for America."
"Her hard work, integrity, and intelligence have earned her a place on this Court," he said. "They gain a colleague who is empathetic, thoughtful, and collegial... Ketanji will interpret the law wisely and fairly, helping that law to work better for the American people, whom it serves."
Roberts said at the ceremony there will be a formal investiture in the fall but the oaths Thursday will allow Jackson to undertake her duties, "and she's been anxious to get to them without any further delay."
Jackson said at the White House after her Senate confirmation, "It has taken 232 years and 115 prior appointments, but we've made it."
"And our children are telling me that they see now, more than ever, that here in America, anything is possible," she said.
Her joining the court also makes it the first time four women will sit on the high court bench at the same time.
President Joe Biden announced in January that Breyer would retire at the end of the term after 27 years on the court, fulfilling the wishes of progressives wary of waiting, and setting off what would become a month-long process to name Jackson and another 42 days for her confirmation.
Three Republicans ultimately joined Senate Democrats in confirming her, marking a significant political win for Biden's long-term legacy -- and his short-term efforts to energize Democrats.
Biden said, when he was considering nominees, that he was looking for someone with Breyer's judicial philosophy and "a pragmatic understanding that the law must work for the American people." And with Jackson's nomination, he delivered on a key promise from the 2020 campaign trail, before the all-important South Carolina primary, that he would nominate the court's first Black woman.
"This is going to let so much sun shine on so many young women, so many young Black women," Biden said in April, alongside Jackson and Vice President Kamala Harris, the nation's first female and first Black vice president. "We're going to look back and see this as a moment of real change in American history."
Jackson, 51, born in Washington D.C., comes off the Court of Appeals for the D.C. Circuit, considered the most important federal court next to the Supreme Court. She has more than eight years of experience on the federal bench, following a path through the judiciary traveled by many nominees before her.
Like other associate justices, she is a graduate of Harvard Law School, but she marks her place in history in multiple ways, as also the first former public defender and first Florida-raised judge to sit on the Supreme Court. She'll also be the first justice since Thurgood Marshall to have criminal defense experience.
Asked what her message to young Americans would be during her Senate confirmations, she recalled to the Senate Judiciary Committee feeling out of place at Harvard in her first semester -- when a stranger provided a remarkable lesson in resilience.
"I was walking through the yard in the evening and a Black woman I did not know was passing me on the sidewalk, and she looked at me, and I guess she knew how I was feeling. And she leaned over as we crossed and said 'persevere,'" Jackson said. "I would tell them to persevere."
She has also spoken with emotion about descending from slaves and her parents growing up in Jim Crow South.
"In my family, it took just one generation to go from segregation to the Supreme Court of the United States," Jackson said at the White House after she was confirmed. "And it is an honor, the honor of a lifetime, for me to have this chance to join the court, to promote the rule of law at the highest level, and to do my part to carry our shared project of democracy and equal justice under law forward into the future."
Her two daughters, Talia, 21, and Leila, 17, were also present for the brief but historic swearing-in.
ABC News Senior Washington Reporter Devin Dwyer contributed to this report.