Nov. 21, 1969: The cover of LIFE magazine features Johnny Cash, who'd just released his "At San Quentin," his second live album recorded before inmates (the first, "At Folsom Prison," was his breakthrough). Wrote LIFE of the king of country music, "He has been fascinated by railroads since childhood when his father would hop freights to look for work." Click through this gallery for more photos and quotes from this classic LIFE cover story.