Outpost 7 was an outpost constructed on an asteroid by Starfleet in 2160. This outpost was one of eight Earth Outpost Stations located in Sector Z-6 along the Federation side of the Romulan Neutral Zone. This zone was a strip of space that acted as a buffer between the Federation and the Romulans in the Alpha Quadrant. (TOS: "Balance of Terror")
This outpost was never mentioned in dialog; this name came from a map of Sector Z-6.