William Philbin was born and raised in Philadelphia, Pennsylvania, where he attended West Catholic High School. His father, Patrick S. Philbin, an Irish immigrant, was a veteran of the Spanish-American War, serving in Cuba and then in the Philippine Islands, where in 1900 he earned the Distinguished Service Cross. After his military service, Patrick Philbin worked as a Philadelphia policeman for 14 years, and then for the Philadelphia post office. William Philbin entered military service during World War II, serving as a chaplain’s assistant to a chaplain of the 16th Infantry Regiment, with which he landed at Normandy, France, on D-Day, earning a Silver Star on the opening day of the invasion.