Armstrong also appeared in the original Broadway cast of Williams' Orpheus Descending and took over the role of Captain Keller in Broadway's The Miracle Worker. His last Broadway appearance was in the short-lived 1960 play The Leon Dream.

He spent many decades working in television and film, including Ride the High Country, The Great White Hope, Predator, Heaven Can Wait, Reds, and Dick Tracy..

He is survived by his five children and five grandchildren.