The show is set in the Milky Way galaxy, roughly during the 2260s. The ship and crew are led by Captain James T. Kirk (William Shatner), first officer and science officer Mr. Spock (Leonard Nimoy), and chief medical officer Leonard McCoy (DeForest Kelley). Shatner's voice-over introduction during each episode's opening credits stated the starship's purpose:
Space: the final frontier. These are the voyages of the starship Enterprise. Its five-year mission: to explore strange new worlds, to seek out new life and new civilizations, to boldly go where no man has gone before.
The series was produced 1966–67 by Desilu Productions, and by Paramount Television 1968–69. Star Trek aired on NBC from September 8, 1966 to June 3, 1969. Although this television series had the title of Star Trek, it later acquired the retronym of Star Trek: The Original Series (Star Trek: TOS or TOS) to distinguish the show within the media franchise that it began. Star Trek's Nielsen ratings while on NBC were low, and the network canceled it after three seasons and 79 episodes. Nevertheless, the show had a major influence on popular culture and it became a cult classic in broadcast syndication during the 1970s. The show eventually spawned a franchise, consisting of five additional television series, 12 theatrical films, numerous books, games, toys, and is now considered one of the most popular science fiction television shows of all time. ... http://en.wikipedia.org/wiki/Star_Trek:_The_Original_Series
List of Star Trek: The Original Series episodes
Memory Alpha (Category:TOS episodes Wiki)
Watch Star Trek (TOS) Episodes on YouTube