Earth Outpost Station
From Memory Alpha, the free Star Trek reference
The Earth Outpost Stations were a series of at least eight outposts, constructed on asteroids, that were located in Sector Z-6, along the Federation side of the Romulan Neutral Zone. They were established by treaty after the Earth-Romulan War of the 2160s, allowing Earth, and later the Federation, to monitor the Neutral Zone.
In 2266, four of the eight outposts came under attack and were pulverized by a powerful high-power plasma weapon utilized by a Romulan Bird-of-Prey. Among the destroyed outposts were Outpost 2, 3, 4 and 8. (TOS: "Balance of Terror")
In 2364, a border outpost reported a contingent of seven Romulan battle cruisers within sensor range. The outpost sent out a distress call, which was responded to by the nearby USS Berlin, however, Starfleet also requested the presence of the USS Enterprise-D in the area was a vital show of force against the Romulans. This was necessary because together, the outpost and the Berlin would have been outgunned by the battle cruisers, had hostilities erupted. (TNG: "Angel One")
By 2367, the Neutral Zone outposts had expanded in number, at least up to Outpost 23. Additional outposts in the region included Outpost Sierra VI. (TNG: "The Defector", "Future Imperfect")
