Walter Cleveland Cowles was born in Farmington, Connecticut, July 11, 1853, Cowles entered the U.S. Naval Academy in July of 1863, at the age of sixteen, graduating in 1867, going immediately to the old Minnesota to the Mediterranean Squadron.  From 1868 to 1870 he was in the old Pensacola and Saginaw in the North Pacific Squadron.  While serving as ensign he came to the Naval Observatory in 1870, and was transferred to the Torpedo Station at Newport in 1871, when he was commissioned lieutenant.  The next year saw him in the practice gunnery ship Constellation; in 1873 he visited the West Indies and Mediterranean, on the Alaska.  Remaining on the same ship, he went to the west coast of Africa in 1874-76, being transferred to the Monocacy in 1977, for four years service on China Station.  The New York Navy Yard had his services for a year in 1881-82 and from 1882 to 1884 he was flag lieutenant of the North Atlantic Squadron.  During this detail he served three weeks on the Isthmus of Panama, guarding the transit across the isthmus and the property of both the Panama Railroad and of American citizens.  He was in command of the Dispatch from1887 to 1891; naval aide to the Secretary of the Navy and in charge of naval militia during 1891-92.  In 1892 he was promoted to Lieutenant Commander, serving as a such until e made naval attaché at London in1893.  In January 1907 he took command of the USS Franklin.

As captain of USS Kentucky (BB-6), he sailed around the world with the Great White Fleet in 1908–1909. He commanded the U.S. Pacific Fleet from 1913 to 1914 and the U.S. Asiatic Fleet from 1914 to 1915.

In March 1915, Cowles became one of the first full admirals in the history of the U.S. Navy when the three commanders in chief of the Atlantic, Pacific, and Asiatic Fleets were all advanced to the temporary rank of full admiral while so serving. Upon relinquishing command of the Asiatic Fleet in June 1915, Cowles reverted to his permanent rank of rear admiral.

Cowles retired in August 1915. He died in Redlands, California, on November 27, 1917.