List of UEG colonies

The Unified Earth Government, between the dawn of interstellar travel in the 2360s and the start of the Great War in 2525, colonised nearly twelve hundred colonies located throughout the Orion Arm of the Milky Way galaxy. This number declined steeply after that date, as the genocidal union of alien species obliterated Human worlds one by one, despite the fiercest armed resistance the UNSC could muster and the ongoing establishment of colonies away from the Covenant axis of advance. By December 2552, the UEG was reduced to just one hundred and forty nine colony worlds, many of them new worlds established since 2525, and only 35 of them inner colonies. During the Remnant War period, the UEG sought to simultaneously reconstruct its shattered interstellar nation-state and to bolster its broken military, following a strategy of only establishing new colonies as the capability to protect them became available.

Inner Colonies
The term 'Inner Colonies' was applied to the two hundred and ten UEG worlds colonised before the date of 2390, when the stringent requirements for passage off-world were relaxed. Inner Colonies in general possessed larger populations, more extensive infrastructure, more developed economies and a focus on service and manufacture-based industries. By comparison, Outer Colonies were less well developed and concentrated on production, agriculture and mining. While generally Outer Colonies were more remote than inner ones, there were exceptions and it was not as simple as their names suggested.