Adam Cartwright , 81 , died at his Hollywood home , his lawyer says . Roberts played Trapper , eldest of `` Bonanza '' Bonanza '' brothers . ( Lorne Greene ) Roberts was civil rights advocate , marched with Martin Luther King , family says . He 's known to younger viewers as post-M*A*S*H Dr. `` Trapper '' Martin Luther King .
Adam Cartwright , 81 , died at his Hollywood home , his lawyer says . Roberts played Trapper , eldest of `` Bonanza '' Bonanza '' brothers . Roberts was civil rights advocate , marched with Martin Luther King , family says . He 's known to younger viewers as post-M*A*S*H Dr. `` Trapper '' Martin Luther King .