Updated: November 14, 2022

In 1967, science fiction editor Arthur W. Saha applied the term "trekkies" when he saw a few fans of the first season of Star Trek: The Original Series wearing pointy ears at the 25th World Science Fiction Convention, on the day series creator Gene Roddenberry showed a print of "Amok Time" to the convention. Saha used the term in an interview with Pete Hamill that Hamill was conducting for TV Guide concerning the phenomenon of science fiction.

And for those who think of themselves as "trekkers", the March 4, 1967 issue of TV Guide Magazine (the first cover appearance of the show), in the "Letters" section there is a letter from a female fan who describers herself as being a member of the Star Trek Underground Watcher's Society. In the letter, she implores her fellow "Trekkers" to not let on that they find the program to be intellectually stimulating, or it will get canceled for sure.

Many early Trekkies were also fans of The Man from U.N.C.L.E. (1964 to 1968), another show with science fiction elements and a very devoted audience. The first Star Trek fanzine, Spockanalia, appeared in September 1967, including the first published fan fiction based on the show. Roddenberry, who was aware of and encouraged such activities, a year later estimated that 10,000 wrote or read fanzines. The mainstream science fiction magazine If published a poem about Spock, accompanying a Virgil Finlay portrait of the Vulcan.

Perhaps the first large gathering of fans occurred in April 1967. When Leonard Nimoy appeared as Spock as grand marshal of the Medford Pear Blossom Festival parade in Oregon, he hoped to sign hundreds of autographs but thousands of people appeared; after being rescued by police, "I made sure never to appear publicly again in Vulcan guise", the actor wrote. Another was in January 1968, when more than 200 Caltech students marched to NBC's Burbank, California studio to support Star Trek's renewal.

The first fan convention devoted to the show occurred on 1 March 1969 at the Newark Public Library. Organized by a librarian who was one of the creators of Spockanalia, the "Star Trek Con" did not have celebrity guests but did have "slide shows of 'Trek' aliens, skits and a fan panel to discuss The Star Trek Phenomenon. Some fans were so devoted that they complained to a Canadian TV station when it preempted an episode in July 1969 for coverage of Apollo 11.

Nothing fades faster than a canceled television series they say. So how come Star Trek won't go away?

However, the Trekkie phenomenon did not come to the attention of the general public until after the show was cancelled in 1969 and reruns entered syndication. The first widely publicized fan convention occurred in January 1972 at the Statler Hilton Hotel in New York, featuring Roddenberry, Isaac Asimov, and two tons of NASA memorabilia. The organizers expected 500 attendees at the "First International Star Trek Convention" but more than 3,000 came; attendees later described it as "packed" and like "a rush-hour subway train". By then more than 100 fanzines about the show existed, its reruns were syndicated to 125 American TV stations and 60 other countries, and news reports on the convention caused other fans, who had believed themselves to be alone, to organize.

Some actors, such as Nichelle Nichols, were unaware of the size of the shows fandom until the conventions, but major and minor cast members began attending them around the United States. The conventions so grew in popularity that the media cited Beatlemania and Trudeaumania as examples to describe the emerging "cultural phenomenon". 6,000 attended the 1973 New York convention and 15,000 attended in 1974, much larger figures than at older events like the 4,500 at the 32nd Worldcon in 1974. By then the demand from Trekkies was large enough that rival convention organizers began to sue each other. The first UK convention was held in 1974 and featured special guests George Takei and James Doohan. After this, there was an official British convention yearly.

Turnout and security at the exhibition are unprecedented with alarm display cases and two full-time guards on hand to protect the memorabilia from overzealous fans.

Because Star Trek was set in the future the show did not become dated, and by airing during the late afternoon or early evening when other stations showed news programs it attracted a young audience. The reruns' great popularity greater than when Star Trek originally aired in prime time caused Paramount to receive thousands of letters each week demanding the shows return and promising that it would be profitable. (The fans were correct; by the mid-1990s Star Trek now called within Paramount "the franchise" and its "crown jewel" had become the studio's single most important property, and Paramount sponsored its first convention in 1996.

The entire cast reunited for the first time at an August 1975 Chicago convention that 16,000 attended. "Star Trek" Lives!, an early history and exploration of Trekkie culture published that year, was the first mass-market book to introduce fan fiction and other aspects of fandom to a wide audience. By 1976 there were more than 250 Star Trek clubs, and at least three rival groups organized 25 conventions that attracted thousands to each. While discussing that year whether to name the first Space Shuttle Enterprise, James M. Cannon, Gerald R. Ford's domestic policy advisor, described Trekkies as "one of the most dedicated constituencies in the country". "Unprecedented" crowds visited a 1992 Star Trek exhibit at the Smithsonian Institutions National Air and Space Museum, and in 1994, when Star Trek reruns still aired in 94% of the United States, over 400,000 attended 130 conventions. By the late 1990s an estimated two million people in the United States, or about 5% of 35 million weekly Star Trek watchers, were what one author described as "hard-core fans".

The Trek fandom was notably fast to use the World Wide Web. The Guardian's Damien Walter joked that "the 50% of the early world wide web that wasn't porn was made up of Star Trek: The Next Generation fansites".