In the middle of the day in Washington DC, Brown Jackson was sworn in by taking the two oaths required to take up the prestigious office.
The oaths were read to HD judge Stephen Breyer, whose place in HD she took over at the same moment, and to HD chief judge John Roberts.
"With all my heart, I accept the solemn responsibility to support and defend the United States Constitution and to practice justice without fear or favor of anyone," Ketanji Brown Jackson said, among other things, according to a statement from the ceremony.
The 51-year-old Brown Jackson was nominated in February by President Joe Biden and approved by the Senate in April this year.
She then called the nomination an honorary assignment "for life".
"We made it"
- It took 232 years and 115 appointments before a black woman was elected to the Supreme Court.
But we made it.
We did it, all of us, she also said after the Senate's approval in April.
However, she takes up her new position during a stormy time - just days after HD's decision to abolish the right to abortion in the country, which led to protests and reactions that spread far beyond the United States.
Jackson, who is considered a liberal, will now be one of the court's nine judges.
Stephen Breyer, 83, who is retiring at his own request, is also a liberal, so the current distribution with six conservative judges and three liberals will not change with the accession of Brown Jackson.
See when Brown Jackson is sworn into the clip above.