Step 1 : Introduction to the question "Which U.S. Supreme Court justice served the longest tenure in the Court’s history?"
...The distinction belongs to William O. Douglas, who served on the Supreme Court for 36 years and 211 days, from 1939 until 1975. Appointed by Franklin D. Roosevelt at just 40 years old, Douglas became one of the most influential—and often controversial—jurists of the 20th century. He developed a reputation for expansive interpretations of civil liberties, a deep commitment to environmental preservation, and a willingness to write bold, independent opinions. His voice helped shape debates that still echo in constitutional law today.
