Blackmun, born in Nashville, Illinois, in 1908, was regarded as a staunch conservative when he joined the nation's highest court as an associate justice in 1970. Widely praised for his scholarly and carefully drafted opinions, Blackmun was initially allied with other Republican appointees on the court, but all that changed in 1973 with the Roe v. Wade decision. Roe v. Wade, which legalized abortion in America, was authored by Blackmun and thus made him one of the most vilified Supreme Court members in U.S. history.
During the 1980s, he became a champion of maintaining a strict separation between church and state and often cast liberal votes in cases pitting individual liberties against governmental authority. By the time he retired in 1994, he was considered the high court's most liberal justice; although he often claimed that the court's politics had changed more than his own. He died in 1999 at the age of 90.
(Note that the Wikipedia entry says that the Senate confimed Blackmun on May 17, but This Day in History claimed May 12. Anyone know which is correct?)