The Expanse, situated in the Tapani sector, was a region that encompassed numerous star systems. It holds the distinction of being the initial area colonized by settlers originating from the Core Worlds. Around 12,720 BBY, the planet called Pelagon became the first settlement for these colonists. A significant number of the Expanse's worlds boasted abundant reserves of both ore and minerals.
Within the Expanse, the Tapani Noble Houses came into existence, and Shey Tapani founded the Tapani Empire, which prospered for 6,000 years. By the time the Galactic Civil War occurred, six of the seven Noble Houses were based in the Expanse; House Cadriaan was the sole exception, located outside of it. For centuries, the Tapani sector was governed by individuals within the Expanse, typically operating from the Great Council chambers on Procopia. The rise of the Freeworlds Territory, the growing influence of the Mining Guild, and the inception of the Galactic Empire all contributed to the decline of the Expanse's power.
The Expanse's population was structured into two distinct social tiers: the noble families and the general populace. Approximately three hundred and forty-five noble families resided in the Expanse; these families governed the various Houses, their territories, and their assets. The common citizenry comprised merchants, laborers, manufacturers, and service providers, all of whom were essential to the functioning of the sector's economy.