Pernell Elven Roberts Jr. (May 18, 1928 – January 24, 2010) was an American stage, film, and television actor, activist, and singer. In addition to guest-starring in over 60 television series, he was best known for his roles as Ben Cartwright's eldest son Adam Cartwright on the Western television series Bonanza (1959–1965), and as chief surgeon Dr. John McIntyre, the title character on Trapper John, M.D. (1979–1986). Wikipedia