Old Earth Union (-1110 to 588)
Interstellar government from -1110 to 588 comprising Terra and the worlds closest to her: Barnard, Calgary, Dismal, Ember, Fenris, Forlorn, Hades, Heiphastos, Inferno, Junction, Loki, Midway, Peraspera, Prometheus, Sirius, and Ys.
Fleet bases were also maintained at Agidda, Markhashi, and Meshan - all within jump-3 of Terra - but these systems were not considered part of the Union proper; Aggida was a balkanized world and thus unable to send representatives to the Union Council and both Markhashi and Meshan had been abandoned during the recession that followed the fall of the Rim Province in -1690.
The OEU was formed in -1110 out of the Terran Mercantile Community as a response to worsening economic conditions. Although experiencing some problems - a short, vicious tradewar with the newly formed Dingir League from -1106 to -1098 put a severe strain on both sides - the Union proved strong enough to defend itself from any serious threat during the rest of the Long Night, and in 588 it was peacefully incorporated into the Imperium.
Non-canon
Most of this article is canonical, but some secondary facts have been interpolated.