John was born on the 7th of February, 1865, in Ballinrobe, Ireland, and his passage to the United States came about after he was allegedly involved in an incident that had the Royal Irish Constabulary after him. He had walked eighteen miles to get on a train to Queenstown where he would earn his trip to the States through work. Later he enlisted in the US Navy on the 20th of July, 1893 as a coal passer and served on the USS Massachusetts during the Spanish-American War and the USS Vicksburg during the Philippine-American War, where he would earn his first Medal of Honor. The citation reads:

On board the U.S.S. Vicksburg, for heroism in the line of his profession at the time of the accident to the boilers, 29 May 1901.

Eight years later, John's actions earned him a second Medal of Honor and the citation reads:

Watertender, serving on board the U.S.S. Salem, for extraordinary heroism in the line of his profession on the occasion of the accident to one of the boilers of that vessel, 13 September 1909.

John continued to serve until 1916, when he retired after twenty-three years in the Navy. When World War 1 began, he chose to reenlist and served in New York for three years. After twenty-six years of service, John lived out his retirement, occasionally returning home to Ballinrobe to visit. A statue was later unveiled on the 4th of September, 2010, of John and the daughter of his nephew had said that when John visited he would give sweets and coins to the children of the town.

John died on the 20th of May, 1938, at the age of 73 and twenty-two years later a US Navy destroyer was launched and named in his honor. The USS John King would travel to Dublin to unveil a plaque in Ballinrobe. John King is buried in the Calvary Cemetery in Hot Springs, Arkansas.