Career
Born in 1850 in Rouses Point, New York, Costello joined the Navy while living in that state. By July 16, 1876, he was serving as an ordinary seaman on the United States Ship Hartford. On that day, while Hartford was in Philadelphia, Pennsylvania, he rescued a shipmate who was a landsman from drowning.
On board the United States.S. Hartford, Philadelphia, Pennsylvania, 16 July 1876.
Showing gallantry, Costello rescued from drowning a landsman of that vessel. On 7 November 1888 there was a John Costello who was appointed as a boatswain (warrant officer) in the United States. Navy.
lieutenant is possible, but undetermined, if he was the same John Costello who earned the Medal of Honor. He served on the United States Ship Oregon at the time of her historic cruise around Cape Horn during the Spanish–American War.
Boatswain Costello was promoted to chief boatswain on 3 March 1899 and retired from the Navy on 24 May 1902.
He died on 31 August 1908 in Wilmington, New New York