First rim

The First Rim is a newer name for the Outer Colonies. It was renamed, along with the Inner Colonies, in the mid to late 26th century as a new class of colonies were replacing the former rugged mining industry of the Outer Colonies, the Second Rim. The Inner Colonies, which gradually became more and more commercial oriented, were renamed the Core. From approximately 2570 through 2700, the First Rim had grown into an industrial mix of slight commercial, agricultural, and advanced metal refining and fabricating. One of the most notable planets of the First Rim, Harvest, has become a quite popular and successful colony since the end of the Human-Covenant War.

Trivia

 * Many people still refer to this area as the mining colonies, a slang name given to the first colonies of this region, or simply the Inner Colonies based on familiarity with the name.