Phi Alpha Delta (ΦAΔ or PAD) is the largest co-ed professional law fraternity in the United States. Phi Alpha Delta has members who are university students, law school students, lawyers, judges, and politicians. It was founded in 1902 and today has over 300,000 initiated members. Approximately one out of six attorneys in the United States is a member of PAD. Five of the sitting Justices of the United States Supreme Court are members of PAD. From 1964 to 1968, Tom C. Clark, Associate Justice of the Supreme Court of the United States, served as Supreme Vice Justice of the Fraternity. Additionally, one of five of all Federal judges and three of ten of all State judges are PAD members. Six U.S. Presidents have likewise been members of PAD.