Today, June 3, in 1969, Star Trek, the impressively famous science fiction television series, aired its final new episode after being canceled by NBC after a three-season run.

Created by Gene Roddenberry, the series is notable for it’s well-known introduction dialogue: “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 aired on NBC from September 8, 1966 to today (but in 1969).

The original run of Star Trek had very low ratings with audiences and was decidedly cancelled after three seasons, totaling 79 episodes. NBC couldn’t have known it at the time, but Star Trek would go on to be a cult classic and popularized sensation. There have been 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. Bummer for NBC.

During the show’s first season, NBC had received more fan letters than any other show they’d aired, but for The Monkees (of course), and when fans got wind of the possible cancellation of the series, with the encouragement of Roddenberry and others, fans flooded NBC with mail. Between December 1967 and and March 1968, NBC received over 1 million pieces of mail and disclosed 112 thousand of those to be from Star Trek fans. Hell, even 200 Cal-tech students marched on NBC’s studios in Burbank to protest Star Trek’s end. Similar protests occurred all over the country. These were smart people who wanted the show to continue forward; scientists, doctors, college students. Usually, fan mail was from, well, not smart people.

NBC tried giving Star Trek a better slot to increase its viewership, but in the end they were forced to cut the budget of the show and eventually cancel it altogether. Fortunately for Captain Kirk and the rest, Star Trek lives on.