He was appointed an assistant attorney general in Missouri in 1974, and later entered private practice there. Thomas grew up in Savannah, Georgia, and was educated at the College of the Holy Cross and Yale Law School. Since 2018, Thomas has been the senior associate justice, the longest-serving member of the Court, with a tenure of over 30 years. Thomas is the second African American to serve on the Court, after Marshall. Bush to succeed Thurgood Marshall, and has served since 1991. Clarence Thomas (born June 23, 1948) is an American lawyer who serves as an associate justice of the U.S.