The Known Galaxy stretches out in all directions one-half of the radius of the Galaxy — an area containing one quarter of the galactic plane. However, because it contains the nucleus and substantial portions of the spiral arms, in volume it contains a far greater portion of the mass and resources of the Galaxy. Although there are certainly civilizations beyond the Known Galaxy, they could not hope to compare with the grandeur of the Republic.
Origins of humans unknown - Core Worlds as homeworlds, but the human Xim the Despot had an empire out in the Mid-Rim before even the Republic was founded.
Other civilizations, such as the Hutts, and various empires, already existed...
'A Galactic Republic, dedicated to peace, swept all before it...'
Role of piracy in causing the Republic...
The Galactic Core is the nucleus of our galaxy. It contains two Regions: the Core Worlds and The Colonies.
The Core Worlds are approximately a sphere at the center of the Galaxy. The Region may be considered to consist of three shells surrounding a core, much like the structure of many terrestrial planets. These shells are the Outer Core, the Mid-Core, and the Inner Core, and they surround the Deep Core. The Mid-Core, in the area of Coruscant, Corellia, and Chandrilla, is the location of the great and ancient homeworlds. Linguistically, the first two worlds, along with others nearby such as Corulag and Corialis, suggest a common origin between their naming and that of "Core" Worlds — this is the true center of the Galaxy. In this shell, the systems are not too far apart and the space between them had been adequately swept free of interstellar debris. These favorable corridors explain how the beings living there swiftly encircled and settled the Core thousands of years before reaching far into the Colonies, even though the Inner Rim is only as distant from Coruscant as the opposite edge of the Core Worlds. Even before settlement of this middle shell was completed, it had spread into the Outer Core. This is not mere exploration and small outposts, mind you — as stated above, humans such as Xim had a name for themselves far out in the Rim in these ancient times, and certainly expeditions had already gone out — but intense settlement into these less closely located systems. At the same time, civilization slowly spread Coreward, but it was centuries or millennia before improved astrogation techniques and computers were able to bring it into the Inner Core in force and root out the remaining piracy in the Core Worlds. Garos IV, for example, was only colonized four thousand years ago, yet is today only four days from Coruscant in hyperspace at x1. The Deep Core, the thick conglomeration of stars and other matter at the very heart of the Core Worlds which has already chaotically rotated about its center several times in galactic history, remains nearly impenetrable to this day. Thus, even the Core Worlds have their frontier.
At some point in all this, as settlement as well as conflict exploded around the Core Worlds and even well beyond them, the Republic was born. Its foundation is the subject of legends of piracy, conflicts, domination, and empires.
With the growth through the Core Worlds growing ever more complete, the various systems calmed down and began to mature, developing the traditions of civilization as old as the Republic, by which they still distinguish themelves today. There were still wars and disputes, but even in these ancient times, the beings of the galaxy held the beliefs in the timelessness, peace, and cooperation of their Galactic Republic. About this time, the Core Worlds began pushing outward and rapidly colonizing worlds, adding to their prestige and wealth. Soon, however, the worlds in this new Region, the outer portion of the Galactic Core, became independent, though they retain the name Colonies. Some of the former colonies even formed there own, as in the initial expansion of settlement in Tapani Sector from the planet Pelagon. Following settlement and independence, the most important factor in the development of The Colonies was when the Core Worlds began exhausting their supplies of raw material. The great demand for external resources for the Core began and has never abated, its effects rippling outward across the Galaxy.
New mining corporations sprouted up across The Colonies and brought with them vast increases in trade and development. When the resources finally played out here as well, the economy of The Colonies largely converted as the Core Worlds had. The systems here are largely similar to the Outer Core, but remain junior partners in prestige and influence. The Colonies, like all Regions outside of the Core Worlds, has a jagged border, but may be approximated by an ellipsoid about the nucleus of the Galaxy. Some of the largest concentrations of wealth and trade are located where the spiral arms of the Rim connect there with the Galactic Core.