A Scots-Irish immigrant, James McHenry determined to make something of his life. Trained as a physician, he joined the American Revolution when war broke out. He then switched to a more military role, serving on the staffs of George Washington and Lafayette. He entered government after the war and served in the Maryland Senate and in the Continental Congress. As Maryland's representative at the Constitutional Convention, McHenry helped to add the ex post facto clause to the Constitution and worked to increase free trade among the states. As secretary of war, McHenry remained loyal to Washingto.