Answer: Justice Oliver Wendell Holmes Jr.
One of the country’s most influential common law judges, Oliver Wendell Holmes Jr. became the oldest justice ever to serve on the U.S. Supreme Court. In 1932, he retired at age 90, 309 days, and he was a member of the court for nearly 30 years. Appointed by Theodore Roosevelt in 1902, he became known for his eloquent dissents, his views on common law, and for his “clear and present danger” opinion in Schenck v. United States. He was the third-most-cited American legal scholar of the 20th century. Holmes fought for the Union in the Civil War before graduating from Harvard and beginning his judicial career. He died in 1935 at age 93.
NOTE: If you guessed Justice John Paul Stevens, you were very, very close. When Justice Stevens retired, he was the second oldest serving justice in the Court’s history at 90 years, 306 days.
The oldest justice currently serving on the U.S. Supreme Court is Justice Ruth Bader Ginsburg. She is 85.