John Parker was born in Lexington, Massachusetts to Josiah Parker and Anna Stone. He was a descendant of Deacon Thomas Parker, founder of Reading, Massachusetts. John Parker was also the grandfather of reformer and abolitionist Theodore Parker. John Parker's experience as a soldier in the French and Indian War (Seven Years' War), at the Siege of Louisbourg and the conquest of Quebec, most likely led to his election as militia captain by the men of the town. He was dying from consumption (tuberculosis), on the morning of April 19, 1775, and had not quite five months left to live.