Star Trek the Original Series Season 1 Episode 1 " The Man Trap " Pictured: William Shatner as Captain James T. Kirk and Leonard Nimoy as Mr. Spock
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Like one of those primitive planets the Enterprise crew would occasionally stumble upon (and where they would have to make sure, thanks to the Prime Directive, not to use their futuristic knowledge and gear to alter the civilization’s normal course of development), the birth of Star Trek seems now to date from an almost prehistoric television era. Creator Gene Roddenberry pitched his space-adventure series to the networks as a “Wagon Train to the Stars,” a nod to the westerns that were still the gold standard in popular TV drama in the 1960s. The special effects were almost comically low-tech—all those toy-chest phaser guns, tin-foil headpieces for the aliens and stock shots of crew members getting jostled in the corridor whenever an explosion rocked the ship. (Seatbelts weren’t required in cars yet, much less spaceships.) The Enterprise never actually landed on any of the planets it visited—crew members were “beamed” there instead—for the simple reason that the special effects would have been too costly.

“Space: the final frontier,” intoned William Shatner in the show’s famous opening, announcing the U.S.S. Enterprise’s five-year mission to explore new worlds, to seek out new civilizations, to “boldly go where no man has gone before.” But the mission ended in 1969 after just three seasons, when NBC canceled the series because of low ratings that today, in the fragmented cable world, would have been hailed as a smash success.

Yet Star Trek had an unlikely rebirth and journeyed on to become the most durable cult hit in TV history. The series got a second wind in syndicated reruns; then came a Saturday-morning cartoon series (with the voices of most of the original cast); then, in 1979, the first of six feature films reuniting the TV crew on the big screen. A sequel to the original series, Star Trek: The Next Generation, debuted in 1987 and became the highest-rated series in syndicated (off-network) television. That was followed by three more TV series and six more movies, featuring both the Next Generation cast and a new set of actors portraying the original Enterprise crew in their younger days. Yet another feature film—the 13th, Star Trek Beyond—will hit theaters in July 2016.

The show was a merchandising bonanza, spawning such items as paperback novelizations of Trek episodes, T-shirts, action figures, models of the starship Enterprise, commemorative coins, video games and Star Trek chess sets. The first Star Trek convention, held at New York’s Statler Hilton hotel in January 1972, drew 3,000 fans; within two years, attendance at the annual get-together had quadrupled. Familiar lines—“Beam me up, Scotty” (which was never actually spoken in precisely those words on the show); “Live long and prosper,” Mr. Spock’s Vulcan valedictory—became national catchphrases. Enthusiasts wrote books analyzing the show’s episodes and ethos; cast members turned out memoirs of their days on the series. The show’s futuristic gadgetry anticipated real-life innovations, such as cellphones and medical scanning technology. NASA originally intended to name its first shuttle craft the Constitution. After Trek fans launched a letter-writing campaign in 1976, the space agency switched to the more popular choice: Enterprise.

But Star Trek was always more than just a sci-fi nerd’s love object. The series was born in the midst of the turbulent 1960s, and its outer-space adventures often reflected and commented on the issues of that divisive decade: the Vietnam War, civil rights, Cold War politics, the budding environmental movement. The show had an idealistic, ’60s counterculture mind-set, imagining a 23rd-century world in which humans had outgrown war and prejudice. “We must learn to live together, or most certainly we will soon all die together” was how Roddenberry, who died in 1991, expressed the show’s message. “Although Star Trek had to entertain or go off the air, we believed our format was unique enough to allow us to challenge and stimulate the audience.” Star Trek proved that an outer-space action show could appeal to our intelligence, tackle serious issues—and, in a troubled time, offer some hope for the future.

Roddenberry, a Texas-born former Pan Am pilot and press officer for the Los Angeles Police Department, began writing scripts in the 1950s for TV shows like Dragnet, Dr. Kildare and Have Gun, Will Travel. A science-fiction buff since junior high school, he had the idea for a series that would mix the anthology format of sci-fi shows like The Twilight Zone and The Outer Limits with a cast of continuing characters—a kind of Gulliver’s Travels of the future, as he once described it.

He took the idea first to program executives at CBS, who quizzed him for two hours about his plans for the show and then told him goodbye and bought Lost in Space instead. He had better luck at NBC, which ordered up a pilot episode. Titled “The Cage,” the show starred Jeffrey Hunter (a feature-film star who had appeared with John Wayne in The Searchers and played Jesus Christ in King of Kings) as a starship captain named Pike who is taken captive on a planet whose inhabitants want to use him to breed a new race. The network rejected the show as “too cerebral” but liked the concept enough to give Roddenberry another chance with a second pilot.

The second go-round featured an almost entirely new cast. Replacing Hunter (who decided that starring in a science-fiction series would be a bad career move), Roddenberry cast William Shatner, a Canadian actor with substantial stage and screen experience, as Capt. James T. Kirk. Joining him on the bridge was a conspicuously international crew: a Scottish chief engineer (James Doohan), a Japanese helmsman (George Takei) and an African-American communications chief (Nichelle Nichols), as well as a nondenominational ship’s doctor, played in the pilot by Paul Fix and later by DeForest Kelley.

Only one cast member remained from the original pilot: Leonard Nimoy, as the half-Vulcan, half-human Mr. Spock. NBC wanted to drop him too, complaining that Nimoy’s pointy ears and sinister eyebrows made him look “satanic.” But Roddenberry insisted on keeping him. “I felt we couldn’t do a space show without at least one person on board who constantly reminded you that you are out in space and in a world of the future,” he said. “NBC finally agreed to do the second pilot with Spock in it, saying, ʻWell, kind of keep him in the background.’” Spock, with his scrupulously logical mind and exotic Vulcan powers, soon became the show’s most popular character.

Unlike most TV shows of the day, which could reuse props and sets from other cop shows or westerns or sitcoms, Star Trek had to create virtually an entire new world from scratch. The layout of the Enterprise was mapped out in detail. Roddenberry obsessed over the verisimilitude of the gadgets, costumes and terminology. Keeping ahead of real-life technology proved to be a challenge. The hand weapons carried by the crew were originally called lasers. When Roddenberry realized that real-life lasers might become commonplace within a few years, he made a last-minute switch and called them “phasers.” “We didn’t want people saying to us three years from now, ʻOh, come on now, lasers can’t do that,’” he explained.

Roddenberry delivered his second pilot in January 1966, and this time NBC picked it up for the fall schedule. Star Trek made its network debut on Thursday night, September 8, opposite My Three Sons and Bewitched. (The first episode was not the pilot but another episode, called “The Man Trap,” in which the crew encounter a vampire-like alien that sucks its victims dry of body salt. NBC wanted a monster.) Initial reaction was not encouraging. “Star Trek obviously solicits all-out suspension of disbelief, but it won’t work,” wrote Variety. “Even within its sci-fi frame of reference it was an incredible and dreary mess of confusion and complexities.”

Ratings were just good enough to win the series a renewal, but by the middle of its second season, NBC was ready to cancel it. A fervent letter-writing campaign from fans persuaded the network to reverse itself—the first recorded instance of an audience campaign saving a doomed TV show. But it was only a temporary reprieve. For its third season, the show’s budget was cut, Roddenberry stepped away from day-to-day involvement, and by most lights the show’s quality declined drastically. By the end of season three, cancellation was a foregone conclusion.

In its three seasons, Star Trek had produced just 79 episodes, but that was enough to sell the reruns in syndication. There they proved amazingly popular, and pressure started to build to bring the series back. Instead, prompted by the success of Star Wars, Paramount (which had acquired the rights to the series from Desilu, the studio that originally produced it) decided to give the Star Trek crew a shot at the big screen. The 1979 feature Star Trek: The Motion Picture was only a middling success, but its 1982 follow-up, Star Trek II: The Wrath of Khan (with Ricardo Montalbán re-creating a villain he had played in a Trek episode from season one), was a hit both with critics and at the box office. The franchise began expanding at warp speed.

The new iterations surpassed the rather crude original series in many ways. Star Trek: The Next Generation, with an entirely new crew and cast headed by Royal Shakespeare Company actor Patrick Stewart (and with Roddenberry back in charge), boasted higher production values and more sophisticated sci-fi plots, not to mention better ratings than the original ever got. And the fourth series, Star Trek: Voyager, which debuted in 1995, rectified one major shortcoming of the earlier versions: for the first time, a woman (Kate Mulgrew) was in command of the ship.

Still, the original series boldly went where few TV shows of its day were going. Its multicultural, multiracial cast was itself a statement on diversity. “Intolerance in the 23rd century? Improbable!” said Roddenberry. “If man survives that long, he will have learned to take a delight in the essential differences between men and between cultures.” When Pravda complained that the international space crew included no representative of the Soviet Union, Roddenberry added Walter Koenig to the cast in season two, as the Russian navigator Chekov.

The space adventures, moreover, were often thinly disguised allegories for very current social problems. In one episode, “Let That Be Your Last Battlefield,” the Enterprise crew encounter a planet, all of whose inhabitants are black on one side, white on the other. Yet they are riven by racial hatred between those who are black on the right half and those black on the left—a stark, if hardly subtle, condemnation of racial prejudice. In the Cold War–themed “A Private Little War,” Kirk faces a dilemma over whether to supply arms to a primitive people engaged in a guerrilla war, to match the guns the Romulans have given to their enemies. In another episode, Kirk is taken captive by the Romulans and held as a spy after the Enterprise strays into the neutral zone—a story inspired by the then-recent North Korean capture of the U.S.S. Pueblo.

“Television was so tightly censored that science fiction was the only way to escape the taboos in politics, religion or anything else that was controversial,” Roddenberry said. “I really don’t consider myself a science-fiction writer, but I’m interested in what’s happening on this planet and what may happen. In our society, we’re treating man less and less like an individual and more like a social organism.”

Roddenberry’s utopian vision was not always reflected behind the scenes. Several writers for the show, among them the prominent sci-fi author Harlan Ellison (who wrote the classic time-travel episode “City on the Edge of Forever”), fumed at Roddenberry’s habit of rewriting scripts so they would conform to his strict conception of the show’s characters and message. Some cast members complained in later years about Shatner’s camera-hogging ego and his jealousy of any co-star (especially Nimoy) who upstaged him with more lines.

Nor did the actors always welcome being typecast for an entire career, forced to reprise their characters for years in front of Trek nerds whose obsessive devotion to the show had its creepy side. Shatner himself expressed it memorably in a Saturday Night Live sketch from 1986. Appearing at a Star Trek convention, TV’s Capt. Kirk gets testy after too many trivia-obsessed questions from fans. “Get a life!” he finally blurts out to the shocked fans—before being chastised by a convention organizer and returning to the microphone to claim that he was, of course, just playing the “evil Capt. Kirk” from the episode “The Enemy Within.”

The fans were relieved. Shatner, in the sketch and real life, seemed resigned to his Kirkian destiny. And Star Trek—the show, the movies, the franchise, the cult—achieved a feat that even a Vulcan mind meld couldn’t have foreseen. It lived long and prospered.

TIME Books

Richard Zoglin is TIME’s theater critic and the author of Hope: Entertainer of the Century. Read more in TIME’s special Star Trek: Inside The Most Influential Science Fiction Series Ever. Available at retailers and at Amazon.com.

Contact us at editors@time.com.

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