Gunsmoke is not the longest running TV show ever. Not even close. It isn’t even the longest running western. Death Valley Days lasted something like 23 years on the air.
Death Valley Days only made 18 years on TV of new episodes being produced (stayed in reruns for 5 more). Gunsmoke owns it for Westerns, and prime time drama. The Simpsons own it for scripted, prime time, animated, and sitcoms. Then there’s various sports and news programs that own the “serious” records.
From Wikipedai:
“The television series (Gunsmoke) ran for 20 seasons from 1955 to 1975, and stands as the United States’ longest-running prime time, live-action drama with 635 episodes.