Outpost 2 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.
In 2266, the Federation lost contact with the base. It was determined, by the USS Enterprise, that the station was destroyed by an unknown vessel that was later discovered to be a Romulan Bird-of-Prey. (TOS: "Balance of Terror", display graphic)