Powhatan Hughes Clarke was born in 1893 at Fort Custer, Montana, the only child of Elizabeth Clemens Clarke and Powhatan Henry Clarke. The elder Clarke, a friend of the artist Frederic Remington and a recipient of the Congressional Medal of Honor for his efforts in the Indian wars, drowned when his son was three months old. Mrs. Clarke soon left Fort Custer for her former home of St. Louis, taking her boy with her. Powhatan Hughes Clarke entered Saint Louis University at the age of twelve and completed the collegiate course in 1913, receiving the AB (Bachelor of Arts) degree. In 1916 he garnered the LL.B. (Bachelor of Law) from the same school and shortly thereafter was admitted to the Missouri bar. In 1917 he entered the Legal Claims Department of the American Automobile Insurance Company in St. Louis.
On April 16, 1917, he volunteered for the Officers' Reserve of the Signal Corps, Aviation Section, U.S. Army. After flight instruction he received his commission as first lieutenant in the Signal Officers' Reserve Corps. In January, 1918, he shipped out for France with the 21st Aero Squadron.
Clarke received further flight training in France but in June 1918 was detached from the Air Service. He was then assigned to various Administrative Labor Companies and in November, 1918, was transferred from the Air Service to the Army Service Corps. On February 5th, 1919, he was appointed Town-Major of St. Nazaire, and two weeks later became Assistant to the Section, Renting Requisition and Claims Office, the entity settling French government claims against the United States for costs incurred by American troops in France.
Clarke sailed for the United States on September 25th, 1919 and was discharged at Camp Dix, New Jersey on October 25th. The commanding officer of the camp supposedly offered him the rank of major in Military Intelligence should he elect to remain in the service, but Clarke preferred to return to St. Louis. In June 1920 he traveled with his family to Gloucester, Massachusetts for a summer vacation, but developed lung trouble after two weeks there. He was taken to Saranac Lake, New York but failed rapidly. He died on August 30th, 1920 and was buried in the Clemens lot in Calvary Cemetery in St. Louis. Doctors attributed his death to a tubercular condition that had remained dormant from his youth until exacerbated by his wartime activities.