James McHenry was born in County Antrim, Ireland, on November 16, 1753, and briefly attended the University of Dublin before receiving a medical education in America at the Newark Academy (Delaware).McHenry began his service to the United States in 1776 as a volunteer medic in the Continental Army. Initially working as a staff member at a military hospital, McHenry would go on to serve as a surgeon in the field of battle and then as an aide to General Lafayette.

McHenry left the Army in 1781 with the rank of major and proceeded to trade his military career for a legislative one, serving as a state senator in Maryland from 1781 to 1783. McHenry went on to serve at the national level as a member of the Continental Congress (1783-1786) and, in 1787, he became a delegate to the federal Constitutional Convention. Following the convention, McHenry returned to state politics for a number of years as a member of the Maryland state assembly (1787-1796).In 1796, President George Washington offered McHenry the position of secretary of war. McHenry accepted and served both Presidents Washington and John Adams before resigning in 1800. Following his resignation, McHenry retired from politics and returned to Maryland, dying in Baltimore on May 3, 1816.