The Mephout system existed within the Mephout Dominion, a sector of Wild Space. It functioned as the native star system for the Mephout, a sentient species.
Exploration of the space surrounding the Mephout system occurred between the years of 1000 BBY and 25 BBY. During the Clone Wars period, not long after the Commerce Guild took control of the planet Ukio, the Mephout system was visible on a galactic map. This map was displayed on a viewscreen at a facility managed by Passel Argente, who was the Magistrate of the Corporate Alliance.
In 4 ABY, Nagai raiders from beyond the galaxy successfully attacked the Mephout system, targeting the Mephout Dominion government. Around 25 ABY, the Mephout system had a population estimated to be between ten million and one hundred million individuals.
The Essential Atlas, a reference book released in 2009 and penned by Daniel Wallace and Jason Fry, was the first source to mention the Mephout system, locating it within grid square H-20. The system made its debut appearance in The Clone Wars: Act on Instinct, a webcomic by Pablo Hidalgo published on StarWars.com during the second season (2009–2010) of the Star Wars: The Clone Wars animated television show.