The birthplace of the human race, Sol (aka. ‘the’ Solar System) was colonised before the First Age of faster-than-light travel, starting with Mars and it’s moons and moving onto the asteroid belt and moons of the gas giants. But even with this new horizon to expand into the human race remained in competition with itself, leading to conflict and upheaval.
The Triton colony was 6 months old when Dr. Elias Kruger and his team made their FTL jump. This sparked a second age of exploration and colonisation, to nearby star systems and beyond.
As humans made baby steps away from Sol, humans consolidated their hold on their home. Built layers of infrastructure, defences and civilisation. The best territory was claimed by the British and American settlers, followed by the European Union, the Asian Coalition and the smaller states. Sol remains home to them, as well as a small group of megacoporations and other groups.
Sol forms the centre of the human Core Worlds, a line of civilisation from Triton all the way back to a terraformed Venus. There is law and order and safety, starkly juxtaposed against the Rimward colonies.