John was born on the 9th of October, 1847 in County Cork, Ireland. In July of 1863, John enlisted in the US Army and claimed to be 18 years old. For those that aren't that quick at math, he was 15 years old at this time and ended up serving with the 16th New York Cavalry Regiment and the 3rd New York Provisional Cavalry Regiment. His enlistment was up in September of 1865 and four years later, John enlisted in the US Marine Corps in Brooklyn, Ny. It was his actions on the 11th of June, 1871 that would earn him the Medal of Honor. The citation reads:

On board the U.S.S. Colorado in action at Korea on 11 June 1871. Fighting hand-to-hand with the enemy, Coleman succeeded in saving the life of Alexander McKenzie.

John stayed in the Marine Corps until he retired in August of 1893 and moved to California. John Coleman died on the 30th of October, 1904 at the age of 57 and is buried in the Mount Hope Cemetery in San Diego, California; division 6, section 2, lot 24, grave 6.