Federation map showing the position of Outpost 1 in relation to Romulus and the Romulan Neutral Zone
Outpost 1 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", display graphic)
Background
This outpost was never mentioned in dialog; this name came from a map of Sector Z-6.
The location of the Romulan Neutral Zone on "The Explored Galaxy" wall chart
"The Explored Galaxy" was a map of charted space in the Alpha Quadrant. The Romulan Neutral Zone was located between the Tholian Assembly and Romulus. Both locations were identified in DS9: "The Search, Part II", "Call to Arms" as being located in this quadrant. The chart, first seen chronologically in Star Trek VI: The Undiscovered Country, was also seen in several Star Trek: The Next Generation and Star Trek: Deep Space Nine episodes set in the 24th century, from the year 2364 to 2370. These were TNG: "Conspiracy", "The Measure Of A Man", "The Emissary", "The Mind's Eye", "The Game", and DS9: "In the Hands of the Prophets", "Cardassians".
According to the Star Trek: Star Charts (pg. 66), there were 23 Earth outposts. Outposts 1 to 8 were mentioned in dialog or were seen on the Z-6 Sector map in "Balance of Terror" and Outpost 23 was mentioned in dialog in "Future Imperfect". Outpost 1 was constructed in an area of space that been contested over during the Romulan War Theater of Operations (2156-2160).}}