As of 2015, there were 635 episodes in the entire Gunsmoke television series. These episodes were released over a time span of 20 years in the 20 seasons of the show.
Gunsmoke first aired in 1955; the first season had a total of 39 episodes. The general trend of the number of episodes per season is negative, it starts at 39 episodes per season and reduces eventually to the 24 episodes per season that are seen in the 16th-20th seasons (1970-1975). Gunsmoke starred the actor James Arness, who played the main character Matt Dillon. Arness was the only actor present in all 635 episodes.