William Maguire received his B.A. from Seton Hall College in Orange, New Jersey, in 1910, and received his M.A. from Catholic University in Washington, Massachusetts, in 1911. In 1915, he completed his theological studies at the University of Louvain in Belgium, and was ordained a Roman Catholic priest on July 15, 1915. His first assignment was as assistant pastor of Immaculate Conception Church in Montclair, New Jersey, until 1917. In 1917 he entered military service in the U.S. Navy, serving as Acting Chaplain aboard the U.S.S. Maine, and then in early 1918 aboard the U.S.S. Texas. He served on the U.S.S. Prometheus (1919) the U.S.S. Idaho (1927), and then at the Naval Training Station at Great Lakes. He returned to sea service in 1923 aboard a succession of ships: U.S.S. Trinity, U.S.S. Bridge, U.S.S. McCormick (1924), and the U.S.S. Arkansas and U.S.S. Black in 1929. Largely a sea-service chaplain, he served on the U.S.S. Mississippi (1933), U.S.S. Indianapolis (1940), and then the U.S.S. San Francisco. He was promoted to Captain in 1941, and during World War II served as Chaplain of the Pacific Fleet, the most senior Naval chaplain. His photograph appeared on the cover of “Life Magazine” on November 2, 1942. He retired in 1946 as a U.S. Navy Rear Admiral.