The Harron Marches, a sector, could be found within the Slice region of the Expansion Region. In the year 0 ABY, the Marches were adjacent to the Belasco sector in the spinward direction. This sector also shared a quadruple border with the Askarian, Circarpous, and Harron sectors along its southern boundary, as well as another quadruple border with the Askarian, Hangshan, and Serathrace sector along its western edge. The Bruvia system, named after the Bruvian people, was located within the Harron Marches.
The creation of the Harron Marches occurred in the StarWars.com Online Companion for The Essential Atlas, a reference book released in 2009. Modi designed a map showcasing the sector, which was then featured in the 2012 StarWars.com article titled "Essential Atlas Extra: Expansion Region."