SG-1 eventually learns that highly evolved human-like beings, known as the Ancients, had originally built the Stargate network millions of years earlier, before ascending to a higher plane of existence, after which they pledged not to interfere in the lives of other species.

The pilot episode ("Children of the Gods"), set one year after the events of the original feature film, introduces the Goa'uld System Lord Apophis (Peter Williams) as the main antagonist when he attacks Earth's mothballed SGC military base through the Stargate and kidnaps an airman.

Earth's flagship team SG-1, which includes Apophis's defected First Prime (lead Jaffa soldier) Teal'c, initiates several alliances with other cultures in the galaxy, such as the Goa'uld-like but truly symbiotic Tok'ra, the advanced human Tollan, the pacifist Nox, the benevolent Roswell-alien Asgard and remnants of the powerful Ancients.

After Apophis's defeat in the Season 5 premiere ("Enemies"), the half-Ascended Goa'uld System Lord Anubis (David Palffy) assumes the role of the primary antagonist of the show.

In the Season 7 finale ("Lost City"), SG-1 discovers a powerful weapon in an Ancient outpost in Antarctica that annihilates Anubis's entire fleet and also sets the stage for the spin-off series Stargate Atlantis.

While the Ori send enhanced human beings named Priors to the Milky Way to convert the galaxy to Origin, Ba'al and some minor Goa'uld infiltrate Earth through The Trust (a coalition of rogue NID operatives) to rebuild their power.

[9] After Anderson accepted the part, Brad Wright and Jonathan Glassner reviewed several thousand taped auditions and invited approximately 25 promising actors to screen tests in Los Angeles.

[20] The producers liked the on-screen chemistry between Black's Vala Mal Doran and Shanks's Daniel so much that they re-introduced her in a six-episode story Arc to cover for the maternity leave of Amanda Tapping at the beginning of Season 9.

[22] The role of the leading man was filled with Ben Browder (also of Farscape fame), who had met with the Stargate producers as soon as the introduction of new main characters for Season 9 was discussed.

[27] Creators Brad Wright and Jonathan Glassner were executive producers and show runners of Stargate SG-1 in the first three seasons, having the final say (besides MGM and the network) on stories, designs, effects, casting, editing and episode budgets.

[32] Martin Wood filmed half a dozen stock shots of the real Cheyenne Mountain complex for use in the series approximately ten days before the premiere of the pilot episode.

His Egyptian look was reflective of the Goa'uld Ra from the feature film and was complemented with a forehead symbol and a gold skin tone, although his make-up process was simplified over the years.

[50] For the look of aliens, the make-up department collaborated with prosthetics companies from Vancouver and Los Angeles, including Steve Johnson's XFX (first three seasons only) & Todd Masters.

According to composer Joel Goldsmith, Stargate SG-1 had a traditional action-adventure score, "with a sci-fi, fantasy flair" that goes "from comedy to drama to wondrous to suspense to heavy action to ethereal".

[59] Since Goldsmith lived a thousand miles away from Vancouver, he and the producers discussed ideas over the phone[61] and exchanged tapes via Federal Express for several years until the show switched to Internet file transfers.

[75] Several scenes of Season 4's "Small Victories" were filmed aboard and outside a decommissioned Russian Foxtrot-class submarine, which had been brought from Vladivostok to Vancouver by a private owner.

[9] The United States Navy invited the cast and producers to film aboard the nuclear submarine USS Alexandria (SSN-757) and at their Applied Physics Laboratory Ice Station in the Arctic for the direct-to-DVD sequel Stargate: Continuum.

[79] Despite the show's extensive intergalactic mythology and science fiction elements, scholar M. Keith Booker considered SG-1 ultimately character-driven and heavily dependent on the camaraderie among the SG-1 members.

[4] The two-hour pilot episode received Showtime's highest-ever ratings for a series premiere with an audience of approximately 1.5 million households in the 8 p.m. Sunday slot of July 27, 1997.

The Sci Fi Channel made its largest single programming acquisition of $150 million in 1998 by buying the exclusive basic cable rights to the MGM package Stargate SG-1, The Outer Limits and Poltergeist: The Legacy.

[34] Since SG-1's ratings were good from a financial standpoint, the Sci Fi Channel picked up MGM's offer to continue the show into a sixth season, yet with a slightly reduced budget.

Brad Wright found it "almost embarrassing" that Stargate SG-1 was much more popular in the United Kingdom than in Canada,[27] where the show aired on Space, Citytv, A-Channel, Movie Central and French-language channels TQS and Ztélé.

[108] While news outlets cited declining ratings, expensive production and lack of promotion as possible reasons for the cancellation,[104][109] the Sci Fi Channel's Mark Stern merely stated the decision was not ratings-based.

[149] Sharon Eberson of the Pittsburgh Post-Gazette, wrote that "Stargate SG-1's place in the sci-fi universe can be measured in longevity, spot-on cast chemistry, rabid fans who call themselves Gaters and the tough subjects it has tackled", going on to note that the show "had rarely been a critical darling".

Wilson appreciatively teased SG-1's format of visiting slightly different, English speaking alien worlds, with similar caves and studio-flat floors, writing that "what makes it good are the jokes, the actors, and the great ideas the writers keep throwing out".

[152] What Culture believed SG-1 to be the best entry into the Stargate franchise, surpassing both the film and spinoff series, putting it #10 on their 25 Greatest Sci Fi TV Shows of All Time list.

Some fans' belief that there was a real Stargate device under Cheyenne Mountain inspired writers Joseph Mallozzi and Paul Mullie to come up with their own conspiracy story for Season 4's "Point of No Return".

[27] MGM executive vice president Charles Cohen described Stargate SG-1 and its spinoff series as the television counterpart of their James Bond franchise, being very profitable and improving their image.

[34] According to Stan Beeler and Lisa Dickson in their 2005 book Reading Stargate SG-1, the only science fiction shows to exceed the staying power of SG-1 are Doctor Who and the Star Trek franchise, although The X-Files and Buffy/Angel might have comparable longevity.

[190] Reflecting on SG-1 in 2020, Dean Devlin, co-creator of the 1994 original film, recalled that initially he had been very hostile to the series, likening his experience of it to "watching someone else raising your child" and pointing out that the full-frontal nudity featured in the pilot episode was not what he thought Stargate should be about.