Eldorado was a planet located somewhere in the space of the galaxy's Alpha or Beta Quadrants, in orbit of the Eldamas 344 star system, at coordinates 2.47S 4.69W.
History and specifics
In the 23rd century, Eldorado was home to a Federation colony that was a center for mining and trade. By reference stardate 2/2306.01, the world had a population of around 1 billion individuals of various races and cultures, chartered as an associate member of the Federation. (FASA RPG module: The Federation)
Eldorado was named for its natural wealth in numerous types of rare minerals, including dilithium deposits. Starfleet maintained a small patrol station here with a squadron of corvettes to discourage pirates. (FASA RPG module: The Federation)