Williams service as ambassador to the Philippines at the end of the Johnson Administration is documented in the Ambassador to the Philippine series. It consists primarily of correspondence of Williams and Jean Campbell, his secretary. Additional information on his activities as ambassador can be found in the series Personal Papers, 1883-1986, subseries schedules (box 94-N) and speeches (box 99-N).
The bulk of the Career/Professional group materials detail Williams' terms as a justice on the Michigan Supreme Court. These materials run to 47 linear feet and are arranged alphabetically by type of material. By mutual agreement between the Michigan Historical Collections and the Supreme Court of Michigan, the case files are closed to researchers. Other files in the Supreme Court series document the administration of the Supreme Court and the state court system and Williams' ability as a reformer in modernizing the Michigan courts.