NBC airs the 19th episode of the military drama The Lieutenant, created and produced by future Star Trek creator Gene Roddenberry and starring Gary Lockwood (2001: a space odyssey) and Robert Vaughn (The Man From UNCLE). 
NBC airs the 19th episode of the military drama The Lieutenant, created and produced by future Star Trek creator Gene Roddenberry and starring Gary Lockwood (2001: a space odyssey) and Robert Vaughn (The Man From UNCLE).
NBC airs the 20th episode of the military drama The Lieutenant, created and produced by future Star Trek creator Gene Roddenberry and starring Gary Lockwood (2001: a space odyssey) and Robert Vaughn (The Man From UNCLE).
NBC airs the 21st episode of the military drama The Lieutenant, created and produced by future Star Trek creator Gene Roddenberry and starring Gary Lockwood (2001: a space odyssey) and Robert Vaughn (The Man From UNCLE). Nichelle Nichols, in her first television acting role, and Dennis Hopper (Easy Rider) guest star in an episode that is pre-empted by some network affiliate stations.
NBC airs the 22nd episode of the military drama The Lieutenant, created and produced by future Star Trek creator Gene Roddenberry and starring Gary Lockwood (2001: a space odyssey) and Robert Vaughn (The Man From UNCLE). Future Star Trek cast members Leonard Nimoy and Majel Barrett guest star; this was Roddenberry’s introduction to Nimoy.
NBC airs the 23rd episode of the military drama The Lieutenant, created and produced by future Star Trek creator Gene Roddenberry and starring Gary Lockwood (2001: a space odyssey) and Robert Vaughn (The Man From UNCLE). Ricardo Montalban (Fantasy Island) guest stars.
NBC airs the 24th episode of the military drama The Lieutenant, created and produced by future Star Trek creator Gene Roddenberry and starring Gary Lockwood (2001: a space odyssey) and Robert Vaughn (The Man From UNCLE).
NBC airs the 25th episode of the military drama The Lieutenant, created and produced by future Star Trek creator Gene Roddenberry and starring Gary Lockwood (2001: a space odyssey) and Robert Vaughn (The Man From UNCLE).
NBC airs the 26th episode of the military drama The Lieutenant, created and produced by future Star Trek creator Gene Roddenberry and starring Gary Lockwood (2001: a space odyssey) and Robert Vaughn (The Man From UNCLE).
NBC airs the 27th episode of the military drama The Lieutenant, created and produced by future Star Trek creator Gene Roddenberry and starring Gary Lockwood (2001: a space odyssey) and Robert Vaughn (The Man From UNCLE). Walter Koenig (Babylon 5) and Neva Patterson (V) guest star.
NBC airs the 28th episode of the military drama The Lieutenant, created and produced by future Star Trek creator Gene Roddenberry and starring Gary Lockwood (2001: a space odyssey) and Robert Vaughn (The Man From UNCLE). Vic Tayback and Denver Pyle (The Dukes Of Hazzard) guest star.
NBC airs the 29th and final episode of the military drama The Lieutenant, created and produced by future Star Trek creator Gene Roddenberry and starring Gary Lockwood (2001: a space odyssey) and Robert Vaughn (The Man From UNCLE). Greg Morris (Mission: Impossible) and James Shigeta guest star in a powerful script written by Roddenberry.
With over two years of development behind it, Gene Roddenberry’s Star Trek finally premieres on NBC with The Man Trap, the completed episode that the network feels most strongly represents the series concept and will connect with a 1960s audience accustomed to police shows and westerns. (It also helps NBC – and its corporate parent, General Electric, who has a stake in the television manufacturing industry – showcase its new season in color.) 
The second episode of Gene Roddenberry’s science fiction series Star Trek airs on NBC. Robert Walker Jr. and Abraham Sofaer guest star.
The third episode of Gene Roddenberry’s science fiction series Star Trek airs on NBC. Sally Kellerman (M*A*S*H) and Gary Lockwood (The Lieutenant, 2001) guest star. This is the second pilot, and shows numerous noticeable differences in casting and costumes, but NBC and Desilu Studios elect to air it anyway, giving the production team time to complete more new episodes.
The fourth episode of Gene Roddenberry’s science fiction series Star Trek airs on NBC. Bruce Hyde guest stars as Lt. Kevin Riley.
The fifth episode of Gene Roddenberry’s science fiction series Star Trek airs on NBC. The episode is written by renowned science fiction writer Richard Matheson, author of the novel “I Am Legend”.
The sixth episode of Gene Roddenberry’s science fiction series Star Trek airs on NBC. Roger C. Carmel guest stars as interplanetary rogue Harry Mudd in the character’s first live action appearance.
The seventh episode of Gene Roddenberry’s science fiction series Star Trek airs on NBC. Ted Cassidy (The Addams Family) and Andrea Jackson guest star.
The eighth episode of Gene Roddenberry’s science fiction series Star Trek airs on NBC. Kim Darby (True Grit) and Michael J. Pollard guest star.
The ninth episode of Gene Roddenberry’s science fiction series Star Trek airs on NBC. Morgan Woodward guest stars.
The tenth episode of Gene Roddenberry’s science fiction series Star Trek airs on NBC. Clint Howard guest stars; this is actually the first episode produced after NBC’s order for the first season of the show.
The 11th episode of Gene Roddenberry’s science fiction series Star Trek airs on NBC. In an effort to save costs, Gene Roddenberry devises a framing story – referred to behind the scenes as “the envelope” – allowing footage from the rejected 1964 pilot episode The Cage to be used within the context of Star Trek’s current cast as a flashback to a previous crew of the Enterprise. Malachi Throne guest stars in the new footage; Jeffrey Hunter and Susan Oliver are seen in the original footage from The Cage for the first time.
The 12th episode of Gene Roddenberry’s science fiction series Star Trek airs on NBC. In an effort to save costs, Gene Roddenberry devises a framing story – referred to behind the scenes as “the envelope” – allowing footage from the rejected 1964 pilot episode The Cage to be used within the context of Star Trek’s current cast as a flashback to a previous crew of the Enterprise. Malachi Throne guest stars in the new footage; Jeffrey Hunter and Susan Oliver are seen in the original footage from The Cage.
The 13th episode of Gene Roddenberry’s science fiction series Star Trek airs on NBC. Arnold Moss and Barbara Anderson guest star.
The 14th episode of Gene Roddenberry’s science fiction series Star Trek airs on NBC. Mark Lenard guest stars, though not in the familiar role of Spock’s father Sarek. This is the first episode of Star Trek to feature the Romulans.
The 15th episode of Gene Roddenberry’s science fiction series Star Trek airs on NBC. Bruce Mars guest stars as Kirk’s Starfleet Academy nemesis, Finnegan.
The 16th episode of Gene Roddenberry’s science fiction series Star Trek airs on NBC. Don Marshall guest stars. This is the first Star Trek episode to show the oft-mentioned shuttlecraft.
The 17th episode of Gene Roddenberry’s science fiction series Star Trek airs on NBC. William Campbell guest stars.
The 18th episode of Gene Roddenberry’s science fiction series Star Trek airs on NBC. This episode, featuring the memorable reptilian Gorn and location shooting at Vasquez Rocks, is one of the best-remembered episodes of the series.
The 19th episode of Gene Roddenberry’s science fiction series Star Trek airs on NBC. This is the first episode to introduce the concept of time travel via a slingshot maneuver around the sun to the Star Trek mythos (it will later be a vital plot point in Star Trek IV: The Voyage Home).