Amy Coney Barrett took the oath on Tuesday that made her a member of the US Supreme Court.
On Monday, the Senate approved the appointment of the nominee Chief Justice nominated by US President Donald Trump, eight days before the presidential election.
The court distributed a photo via Twitter showing Barrett taking the oath with his hand on the Bible.
The judge, known as a conservative, succeeds the deceased Chief Justice Ruth Bader Ginsburg in the Supreme Court. She belonged to the progressive camp within the court.
The Democrats had to grind their teeth to see how Trump and his Republicans were able to nominate their own candidate for life at the last minute.
With the appointment of Barrett, the conservative majority in the Supreme Court grows to 6 to 3. Barrett, 48, becomes the youngest member of the court and can remain there for decades.