As of the end of 2023, the U.S. Supreme Court comprises nine justices with lifetime appointments. The Court's composition includes:

1. Chief Justice John Roberts (appointed 2005)
2. Justice Clarence Thomas (appointed 1991)
3. Justice Samuel Alito (appointed 2006)
4. Justice Sonia Sotomayor (appointed 2009)
5. Justice Elena Kagan (appointed 2010)
6. Justice Neil Gorsuch (appointed 2017)
7. Justice Brett Kavanaugh (appointed 2018)
8. Justice Amy Coney Barrett (appointed 2020)
9. Justice Ketanji Brown Jackson (appointed 2022)

The makeup of the U.S. Supreme Court plays a crucial role in shaping the country's legal landscape and has a significant impact on American society. The lifelong appointments of the justices mean that any changes in the Court's composition, due to retirement, death, or impeachment, can lead to substantial and enduring influences on both legal and societal matters in the United States.