Murray found himself in the thick of the New York and New Jersey campaign. He saw action at the Battle of White Plains in October 1776, after which he was promoted to captain, as was his friend, and fellow lieutenant of the Maryland Line, James Monroe. While serving at New York he suffered severe hearing loss from a bursting cannon while firing at a British fleet making its way up the North River (the lower Hudson along the west side of Manhattan). Murray served in the Army until the end of 1777, when he returned home on sick leave.