William Daniel Leahy was born May 6, 1875, in Hampton, Iowa, to lawyer Michael A. and Rose Hamilton Leahy. In later years his parents lived variously at Ashland, Wausau, and Marshfield, Wisconsin. His father was a graduate of the University of Wisconsin (1862), and was captain of the 35th Wisconsin Infantry Regiment during the Civil War period, 1862-1866. Leahy himself graduated from Ashland High School in 1892, and entered the U.S. Naval Academy in May 1893 from the Ninth Congressional District of Wisconsin.
Commissioned an ensign in the U.S. Navy in 1899, Leahy advanced to the rank of admiral and the post of Chief of Naval Operations, 1937-1939. He served in the Spanish-American War, the Philippine Insurrection, and the Boxer troubles; was chief of staff in the Nicaraguan Occupation in 1912 and the Haitian campaign in 1916; commanded the USS Dolphin during the Mexican punitive expedition in 1916; and served as a commander during World War I.
Leahy retired from the Navy, August 1, 1939, and was appointed governor of Puerto Rico. From 1940 to 1942, he served as ambassador to France. In July of 1942, he became chief of staff to the Commander-in-Chief of the Army and the Navy, a post he held until 1949.
Leahy married Louise Tennent Harrington, February 3, 1904, and they had one son, William Harrington Leahy, who also pursued a naval career. Mrs. Leahy died April 21, 1942. Admiral Leahy died July 20, 1959, and was buried in Arlington National Cemetery.
