Like all Hollywood pitches, Roddenberry had to relate his show premise to an already successful franchise in order to interest production studios. Thus, Star Trek was floated to TV houses as "Wagon Train in space" -- a description that many fans consider inaccurate, and perhaps even condescending.
In truth, Roddenberry was only citing the episodic, random-encounter-with-the-unknown aspect of Wagon Train. His inspiration for Star Trek, as he would later claim, was actually one of the most famous works of classic literature ever written.
What work of classic literature was Gene Roddenberry's self-professed inspiration for Star Trek?