William Joseph Brennan Jr. was born on April 25, 1906, to Irish immigrant parents in Newark, New Jersey. He pursued his education in economics at the University of Pennsylvania before attending Harvard Law School. After entering private legal practice in New Jersey, he served in the U.S. Army during World War II, showcasing his commitment to his country.
In 1951, Brennan was appointed to the Supreme Court of New Jersey, marking the beginning of his significant judicial career. His ascent to the U.S. Supreme Court came in 1956 when President Dwight D. Eisenhower appointed him through a recess appointment, a move that was confirmed by the Senate the following year. Brennan would go on to serve as an Associate Justice until his retirement in 1990, making him the eighth-longest serving justice in the Court's history.
Throughout his tenure, Brennan was a prominent figure in the Court's liberal wing, known for his progressive views. He was a staunch opponent of the death penalty, dissenting in over one thousand four hundred cases where the Court declined to review death sentences. His advocacy extended to abortion rights and gay rights, reflecting his commitment to civil liberties.
Brennan authored several landmark opinions that shaped American law, including Baker v. Carr, which addressed legislative district apportionment, and New York Times Co. v. Sullivan, which established the standard of