Born in 1841 in Baltimore, Maryland, Cadwallader was living in Frederick, Maryland when he enlisted in the Army in May 1861. He served as a corporal in Company H of the 1st Regiment Maryland Volunteer Infantry. During the Battle of Hatcher's Run in Virginia on February 6, 1865, Cadwallader "[g]allantly planted the colors on the enemy's works in advance of the arrival of his regiment." For this action, he was issued the Medal of Honor several decades later, on January 5, 1897.