Although it started out as a half-hour show, it was expanded to an hour beginning with its seventh season. "Gunsmoke" was one of two TV series that introduced the "adult western" to television audiences. (The other was "The Life and Legend of Wyatt Earp," which premiered the same week). Prior to "Gunsmoke," shows depicting the wild west were conceived around fantasy characters, such as the Lone Ranger and Hopalong Cassidy, holdovers from movie and radio serials.
"Gunsmoke" centered around the exploits of Dillon (James Arness) in the frontier town of Dodge City, Kansas in 1873. His kindly companion was Doc Adams (Milburn Stone), the town physician who spent many hours chugging beers at the Longbranch Saloon, owned and operated by the shapely Kitty Russell, who was always attracted to the marshal (but never actualized this into a romance).
"Gunsmoke" started the trend for TV westerns, which ultimately led to there being 30 of them on the air at one time. However, it outlasted all of them and at the time of its cancellation in 1975, it was the only show of its kind still on the air.