Dr. William Clausen Pettijohn, 87, of Show Low, Arizona, passed away on August 8,2011, of heart conditions. Dr. Pettijohn was born in Twin Falls, Idaho, on August 2, 1924. He served in the United States Army in the Pacific Theater in WWII on the headquarters staff of General Douglas MacArthur. After the war, he received an undergraduate degree from the University of Idaho and a Master's Degree from the American Graduate School at the University of Copenhagen, Denmark, where he met and married a fellow graduate student, Ruth Hansen, in 1950. Dr. Pettijohn went on to receive a Ph.D in Philosophy from the University of Edinburgh in Scotland. Upon returning to the United States in 1953, he was on the academic faculty at Yale University and subsequently at Carleton College, Minnesota, before joining the Operations Research Institute at Johns Hopkins University in Baltimore, Maryland. He then moved on to become Stanford Research Institute's civilian chief of the Combat Development Experimentation Command at Fort Ord, California. As a result of his contributions, Dr. Pettijohn was awarded the Outstanding Civilian Service Medal from the Department of the Army. In 1967, Dr. Pettijohn's career returned him to Washington, DC, where he served in the Pentagon under Secretary of Defense Robert McNamara. Subsequently, Dr. Pettijohn formed the Vertex Corporation, a defense and technology consulting firm based in Washington, DC., where he acted as president until his retirement in 1988. Dr. Pettijohn and his wife Ruth enjoyed sea kayaking and horseback riding. They also shared a love of living in historic homes including Terra Rubra Farm, the birthplace of Francis Scott Key. Dr. Pettijohn is survived by his wife of 61 years, Ruth Pettijohn of Show Low, Arizona; daughters: Susan Pettijohn and Lise Pettijohn of Snowflake, Arizona, Carley Fortier of Washington, DC; son: Garth Pettijohn of Malibu, California; and grandchildren Kelsey Pettijohn and Dyer Pettijohn of Malibu, California. No services are planned at this time.