The Earth Outpost Stations were a series of military installations set up by United Earth following the Earth-Romulan War to monitor Romulan activity along the Neutral Zone and to detect any potential incursions. The Earth Outpost Stations remained in operation following the establishment of the United Federation of Planets in 2161. In 2266, a number of Earth Outpost Stations were destroyed during a Romulan incursion into Federation space that ended post-war Romulan isolationism. (TOS episode: "Balance of Terror")