Worthington was born near Johnstown, Pennsylvania, but spent his childhood in Ohio. He came to Kentucky with his parents as a teenager, and served in the 22nd Kentucky Infantry Regiment of the Union Army during the American Civil War. He was commissioned captain of the Company B of the regiment, and was later promoted to the ranks of major and lieutenant colonel. Worthington was present during the Siege of Vicksburg and the Battle of Cumberland Gap. He was under the command of Ambrose Burnside during the Red River Campaign and at the Capture of New Orleans.