​From Wikipedia, the free encyclopedia Pernell Elvin Roberts, Jr was an American stage, movie and television actor as well as singer. In addition to guest starring in over 60 television series, he was widely known for his roles as Ben Cartwright's eldest son, Adam Cartwright, on the western series Bonanza, a role he played from 1959 to 1965 — and as chief surgeon Dr. John McIntyre, the title character on Trapper John, M.D. (1979–1986). He was also widely known for his life-long activism, which included participation in the Selma to Montgomery marches in 1965 and pressuring NBC to refrain from hiring whites to portray minority characters. Description above from the Wikipedia article Pernell Roberts, licensed under CC-BY-SA, full list of contributors on Wikipedia.