 Of the justices currently sitting , the youngest at time of appointment was Clarence Thomas , who was 43 years old at the time of his confirmation in 1991 . As of the beginning of the 2014 – 15 term , Elena Kagan was the youngest justice sitting , at 54 years of age . The oldest person to have served on the Court was Oliver Wendell Holmes , Jr . , who stepped down two months shy of his 91st birthday . John Paul Stevens , second only to Holmes , left the court in June 2010 , two months after turning 90 . 
