(covers information from several alternate timelines)
The Eminiar system was a planetary system in the Alpha Quadrant. This system was located within the star cluster NGC 321. The system's primary was named Eminiar. A planet in this system, Eminiar VII, was inhabited by a native species. This species had colonized the third planet in this system, Vendikar, sometime prior to the late 18th century. (TOS: "A Taste of Armageddon"; Star Trek VI: The Undiscovered Country, production art)
Its location in the Milky Way Galaxy was depicted on a Federation star chart in 2293. (Star Trek VI: The Undiscovered Country; production art) In 2367, the same chart was used in the prime timeline in Captain Benjamin Maxwell's ready room on the USS Phoenix. (TNG: "The Wounded" display graphic)
USS Valiant made first contact with the Eminians in 2217, but was destroyed before it could leave the system. Between 2247 and 2267 thousands of Federation lives were lost in the quadrant where the Eminiar system was located. Their lives could have been saved had the Federation had a treaty port in the area.
In 2267, the Federation wanted desperately to open diplomatic relations with the Eminiar system. Upon approach, Eminiar VII issued a code 710 warning - stay away at all costs. The actions of the crew of USS Enterprise effectively ended the war, and Ambassador Robert Fox assisted the planets in negotiating a peace treaty. (TOS: "A Taste of Armageddon"; ENT: "In a Mirror, Darkly, Part II" display graphic)
By the late 24th century, Eminiar VII had become a tourist destination for Federation citizens. A view of the surface of Eminiar VII was depicted on several viewscreens on Deep Space 9's Promenade and Replimat advertising a trip to the "scenic Eminiar VII". (DS9: "The Muse", "What You Leave Behind")