(covers information from several alternate timelines)
In 2285, the USS Enterprise returned to Spacedock after serving as a cadet training ship on an ill-fated mission in which Khan's plan to steal the Genesis Device and kill Admiral James T. Kirk for revenge was thwarted. At Spacedock, the Enterprise was to be decommissioned, rather than repaired. Kirk – with the help of Captain Scott as well as Commanders Uhura, Sulu and Chekov – stole the Enterprise to rescue Spock's body from the Genesis Planet. The USS Excelsior attempted to give chase, but had been sabotaged by Captain Scott, and "stalled" when it attempted to jump to transwarp just outside the station. (Star Trek III: The Search for Spock)
In 2286, an unknown probe entirely disabled Spacedock upon reaching Earth. The shutdown happened before any vessels within, including the Excelsior, could be launched, resulting in the equally powerless vessels being trapped behind the space doors. When Kirk and his crew had resolved the crisis, power was restored as the probe left the planet. Kirk was demoted to captain, and offered command of a starship – namely the USS Enterprise-A, which was docked within Spacedock. (Star Trek IV: The Voyage Home)
After a brief shakedown cruise, the Enterprise-A returned to Spacedock while Captain Scott worked to resolve design flaws made apparent by the ship's maiden voyage. In 2287 the starship ultimately departed in a hurry, while repairs were still underway, to deal with the crisis on Nimbus III, with the final shuttlecraft carrying the command crew back from shore leave rendezvousing with the ship after it had cleared the station. (Star Trek V: The Final Frontier)
The Enterprise-A was moored at Spacedock prior to an ill-fated trip to escort Klingon Chancellor Gorkon to a peace conference on Earth in 2293. Kirk ordered a departure from the facility at impulse speed, despite the fact that regulations specified thrusters only while inside the structure. Although Lieutenant Valeris, the ship's helmsman, initially questioned the captain's order, she successfully performed the departure and later admitted she had "always wanted to try that."
- See: Spacedock personnel
In script sources, this facility is most commonly known simply as "Spacedock", with an emphasis on the term being capitalized.
Spacedock was imagined as having a total height of over three miles. At that size, the facility could easily be visible with the naked eye from the surface of Earth. (text commentary, Star Trek III: The Search for Spock (Special Edition), DVD)
Although windows providing a view of Spacedock's interior docking bay appear only in Star Trek III: The Search for Spock, they were also originally intended to be seen in Star Trek IV: The Voyage Home as well, with cheering audience members gathered by them. (The Making of the Trek Films, 3rd ed., p. 64)
It was not made clear on-screen whether the facility featured in "Non Sequitur" was intended to be the same spacedock as seen in the films, as the Star Trek Encyclopedia speculates. The only view of the station in the Star Trek: Voyager episode is of a set of doors, themselves stock footage of the Dyson sphere doors from Star Trek: The Next Generation's "Relics".
Star Trek: Starship Spotter describes Earth's Spacedock, the first of it's design, as being conceived during conflicts with the Klingon Empire, approved in 2259, and completed in 2276, with enlargements to two entry doors in the mid-24th century to accommodate larger vessels such as the Galaxy-class. Their specifications, as of 2290, include an overall length of 4,600 meters, overall beam of 4,600 meters, overall draft of 6,900-6,950 meters, crew complement of 76,625 (crew, civilians and transients.) Typical support craft include 285 workbees, 100 shuttlecraft of various types, and 50 Danube-class runabouts. (pp. 72-73)
In the game Star Trek Online, this station was replaced with another sometime before the year 2409. However, the new design was not popular amongst players, and there were many calls for it to be replaced with the classic facility. For STO's first anniversary, on 2 February 2011, the developers replaced the new Spacedock with the original station, explaining it as being the work of Q. Though the external model, as visible from space, appeared to be the classic Spacedock, the interior area, which served as a major player hub, remained based on the original, launch design. With the release of the game's Season 9 update, the Earth Spacedock received a second revamp to correct that inconsistency, with the interior area receiving a major redesign to be more appropriate to the scale and presumed layout of station. The change was justified in the story via the mission "Surface Tension", in which the Undine caused severe damage to the station during their attack on Earth, necessitating extensive repairs and relocation of player activities to a different area.