Pennsylvania | University of Pennsylvania | Society of Jesus | Royal Society | National Geographic Society | American Cancer Society | Pennsylvania State University | Pennsylvania Railroad | Harrisburg, Pennsylvania | Pennsylvania House of Representatives | Erie, Pennsylvania | Carlisle, Pennsylvania | Royal Television Society | Williamsport, Pennsylvania | American Physical Society | Scranton, Pennsylvania | West Chester, Pennsylvania | Montgomery County, Pennsylvania | Lancaster, Pennsylvania | Bethlehem, Pennsylvania | American Chemical Society | International Society for Krishna Consciousness | Hershey, Pennsylvania | American Society of Civil Engineers | Royal Society of Canada | York, Pennsylvania | Royal Geographical Society | Pennsylvania Turnpike | Pennsylvania Academy of the Fine Arts | American Philosophical Society |
A Republican and a Presbyterian, Clark was also a member of the Naval Historical Foundation, the Historical Society of Pennsylvania, the Pennsylvania Genealogical Society, and served as vice president of the Illinois chapter of the Sons of the American Revolution.