At a time when attention spans are shorter than ever, the world's longest-running TV shows stand out as the ultimate test of endurance.

From cult favorites that outlasted entire networks to series that launched icons and became multi-generational staples, the 20 longest-running TV shows show how different genres have endured.

CBS’s radio and television Western, which starred the iconic Marshal Matt Dillon (portrayed by James Arness), first premiered in 1955 and officially ended in 1975. With a total of 635 episodes across 20 seasons, Gunsmoke was crowned the longest-running western in TV history (EBSCO) and scooped up 15 awards (per IMDb). Ironically, the award-winning show was scheduled to be cancelled in 1967 due to low ratings, but CBS President and Gunsmoke fan William Paley ultimate

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