Stargate Atlantis (often abbreviated as SGA) is a Canadian-American science fiction television series and part of MGM's Stargate franchise. The show was created by Brad Wright and Robert C. Cooper as a spin-off series of Stargate SG-1, which was created by Wright and Jonathan Glassner and was itself based on the feature film Stargate (1994). The first three seasons of Stargate Atlantis were broadcast by The Sci-Fi Channel and The Movie Network, while the final two seasons aired exclusively on Sci-Fi.

The show premiered on July 16, 2004; its final episode aired on January 9, 2009. The series was filmed in and around Vancouver, Canada. The story of Stargate Atlantis follows the events of Stargate SG-1's seventh season finale episode "Lost City", in which the cast of that series discovered an outpost created by the alien race known as the Ancients in Antarctica. In the pilot episode, Stargate Command sends an international team to investigate the outpost, where Dr. Daniel Jackson discovers the location of the legendary city created by the Ancients, Atlantis.

The series was a ratings success for the Sci Fi Channel, and was particularly popular in Europe and Australia. Although it received little critical response, Stargate Atlantis was honored with numerous awards and award nominations in its five-season run. After Stargate Atlantis was canceled, the show's co-creators began working on the already conceptualized Stargate Universe which the network had approved to have a bigger budget, be less mythology dependent, and have more focus on character development. 
 

Stargate Universe was released on October 2, 2009, and then canceled after just two seasons. Merchandise for Stargate Atlantisincludes games and toys, print media and an original audio series. With the cancellation of Stargate Universe, the intended direct-to-DVD film entitled Stargate: Extinction has been shelved indefinitely.

The character most difficult to cast was the then-called Dr. Ingram, an unexcitable scientist expert on the Stargate. As the first day of shooting drew nearer and they were unable to find the right actor, they came to realize they had brought in the wrong character. Longtime Stargate director Martin Wood and Brad Wright thought it should be Dr. Rodney McKay, who had already appeared in a guest role in three episodes of Stargate SG-1.

Actor David Hewlett was contacted and arrived at the set the day after filming had started. Dr. Ingram had already been written in to the pilot episode of the show and so the same script was used and the character's name simply changed to McKay. Later scripts were written with Dr. McKay in mind. The creators found themselves with a problem with the character of Lt. Aiden Ford (Rainbow Sun Francks) in season two, a first season regular that the producers, and the actor himself, felt had not worked as intended and was highly underused as a result. Unwilling to write him out, the writers came up with an idea to make the character more important, but that downgraded him to recurring. 

To replace him, they created Ronon Dex as a sidekick for Lt. Col. John Sheppard, but finding an actor with the physical presence and the acting ability necessary was not easy until they saw Jason Momoa's tape. X-files veteran Mitch Pileggi and Kavan Smith were added to the cast in the recurring roles of Col. Steven Caldwell and Maj. Evan Lorne. Paul McGillion's character, Dr. Carson Beckett, became a regular in season two.

Seasons three and four changed the cast lineup again. Paul McGillion's Dr. Carson Beckett was killed in the season three episode "Sunday", then brought back at the end of season four as a recurring character. The new medical chief was Jennifer Keller, played by Jewel Staite, who was introduced in the Season 3 finale, was a recurring character in Season 4, and became a regular in Season 5. Jewel Staite had already played a guest role in Season 2 as Ellia, a female Wraith, and the producers agreed they wanted her for a more important role.

Amanda Tapping's Samantha Carter crossed from Stargate SG-1 for 14 episodes in Season four, as the new leader of the expedition, while Torri Higginson's Elizabeth Weir became a recurring character in season four instead of a regular. Robert Picardo became a regular in season five as Richard Woolsey replaced Samantha Carteras the commander of the Atlantis Expedition. Higginson declined to appear as a guest star; instead, her character Weir was portrayed by Michelle Morgan.

Premise:

Stargate Atlantis follows the present-day adventures of Lt. Colonel John Sheppard and his military team from Earth that, along with two dozen other teams, explore distant planets in the Pegasus Galaxy. They use an alien device known as a Stargate that was built millions of years ago by an advanced race of humans known as the Ancients. The expedition is based in the Lost City of Atlantis on the planet "Lantea". The city was built millions of years ago by the Ancients.