The colony designated X-18999 was funded and constructed by Dekim Barton's Foundation. Originally, the United Earth Sphere Alliance planned to use it as a military colony. Its construction was scheduled to be finished by A.C. 189.
In A.C. 188, a riot led by Quinze took place there, however, Dekim was the true mastermind behind the riot, and his real intention was to lure out and kill Odin Lowe, Heero Yuy's assassin, who was hired by Dekim to assassinate Brigadier General Septum of the UESA. After Lowe's death at the hands of Dekim, the military base inside the colony was destroyed by Lowe's assistant, a nameless boy who goes by the pseudonym Odin Lowe Junior. After the riot, the UESA closed its base, repaired the colony and paid the people of the colony full reparations to compensate for the damages caused.
After the Eve Wars, the citizens of X-18999 secretly allied themselves with the Mariemaia Army, diverting the reconstruction budget given to them by the Earth Sphere Unified Nation into the construction of Serpent mobile suits. Unbeknownst to them however, X-18999 became the colony that filled the main part of the strategy behind Dekim Barton's version of Operation Meteor, which would have resulted in the death of the colony's entire population.
In A.C. 196, the colony requested the ESUN to increase their reconstruction subsidies, and Relena Darlian arrived at the colony for negotiations. Unbeknownst to her, the meeting was actually a trap laid by the Mariemaia Army, and she was captured and held hostage. Dekim Barton intended to drop the colony and place Mariemaia Khushrenada as a figurehead through which he could rule the planet. X-18999 and its population were saved from a horrid demise through the efforts of Trowa Barton, Heero Yuy and Duo Maxwell.