John was born on the 24th of July, 1828, in Dublin, Ireland. While not much is known about his life, we do know that he had joined the US Navy in 1845 and that he displayed actions twice that would earn him the Medal of Honor during the American Civil War. The citations read:
On board the U.S.S. Brooklyn during action against rebel forts and gunboats and with the ram Tennessee, in Mobile Bay, 5 August 1864. Despite severe damage to his ship and the loss of several men on board as enemy fire raked her decks from stem to stern, Cooper fought his gun with skill and courage throughout the furious battle which resulted in the surrender of the prize rebel ram Tennessee and in the damaging and destruction of batteries at Fort Morgan.
Served as quartermaster on Acting Rear Admiral Thatcher's staff. During the terrific fire at Mobile, on 26 April 1865, at the risk of being blown to pieces by exploding shells, Cooper advanced through the burning locality, rescued a wounded man from certain death, and bore him on his back to a place of safety.
John received the Medals of Honor on the 31st of December, 1864 and on the 29th of June, 1865. His service in the Navy ended in 1866 as a Quartermaster and John Laver Mather Cooper died on the 22nd of August, 1891 at the age of 63 and is buried in the Cypress Hills National Cemetery in Brooklyn, New York: Section 2, Site 5022.