Although I'm not sure exactly in what format I'll eventually be presenting this formally, I'm using this post to "noodle" a bit with some setting Bible concepts, mostly for the purpose of establishing context. I don't want to go all "Wookiepedia" on this, though. Keep in mind that during the first Star Wars movie, pretty much all of the context that we get is that 1) there used to be a Republic served by the Jedi order as some type of peacekeeper or somewhat. 2) Now there's an Empire, and a resistance that attempts to overthrow them. 3) There's an Imperial Senate, yet also ranks and nobility like princesses and stuff. 4) The Empire disbands the Senate. 5) Darth Vader was a Jedi knight, but he betrayed and murdered the Jedi Knights.
Now, granted, you can glean a handful more details out of the movie than just that, but not many. That's really kinda it. Much of the context around Star Wars was either developed in the Expanded Universe, or during the prequels. There's less context than you need. This is especially true for folks coming out of the RPG hobby, where big time-lines and detailed campaign settings are the norm. In reality, most of that is completely unnecessary. Maybe even detrimental.
But I want to create a little context.
c. 10,000 B.C. through c. 2050 A.D. Gray aliens abduct numerous people from Earth and resettle them on various planets throughout much of the galaxy, in an inscrutable experiment that lasts millennia. Because of this, genetically pure humans are the largest species throughout the Known Sectors by far, outnumbering everyone else combined at least four to one. However, the long separation combined with responses to alien environments, climates, food sources, etc. have caused a proliferation into an extremely wide array of distinct ethnic groups, many of which now feature exotic (from the perspective of an Earthman) features such as skin, hair and eye color, and even other features.
2060 A.D. Following the recovery of a crashed Gray spacecraft, a team of European and American scientists manage to reverse engineer some of the technology that will become the core of space travel; artificial gravity and primitive bulk drives, which allow the piecing of the "skin" of the brane, allowing temporary travel through the bulk before reentering the brane at another point in space. These early bulk drives allow only relatively small bulk jumps which take several days, but over the next millennia, these are improved somewhat. Bulk jumps that allow the travel of tens of light-years over only about a week's worth of time and a single refueling are now common. (Keep in mind that this is still quite limited. Unlike in Star Wars, where you can travel to hyperspace and end up on the other side of the galaxy in just a few minutes, bulk jumps allow crossing the Local Bubble over the course of many months. The entirety of the Known Sectors is only about 2,500 light years across by 800 light years wide, making up a significant portion of the Orion Spur and a portion of the Sagittarius Arm adjacent to it, with a number of filaments and bridges that connect the otherwise vast and uncrossable gulf between the arms. If one were to travel as quickly as he were able, doing nothing but travel, from one end to the other of the Known Sectors, it would still take almost the entirety of an average lifetime to do so.
c. 2075 through 2125 A.D. As political and economic conditions continue a several century long slide, large numbers of settlers from America and northern Europe in particular left Earth in bulk drive arks to seek their fortunes elsewhere. Upwards of 15% of the entire population of these areas eventually leave Earth as conditions deteriorate into increasingly unstable banana republics caused by the rule of totalitarian globalists who dilute and degrade the physical and human capital of the nations that they rule. Near the end of this period, Russia and China also attain bulk drive technology and send some settler arks of their own. At the end of the period, conditions on Earth have deteriorated so badly that nobody else is able to marshal the resources to send any more arks, and Earth degrades into a stagnant, technologically impoverished backwater. Over the next few centuries, Earth is declared a quarantine zone by nearly every major interstellar colony, and some even forget their origin from Sol. As for the inhabitants of Earth itself, they soon forget that millions of people left to seek their fortunes in the stars.
Starting from this point on, Earth completely ceases to play any role in the setting as it evolves. It's location is hidden or lost, it becomes uncharted, and the colonists who originated there do not look back.
2125 through c. 2500 A.D. The various settler arks arrive at their destinations and establish colonies. In the beginning, some were supplemented by further arks, but those soon tapered off. Most, however, grew organically very quickly, as large families meant more hands to help with the large quantity of work that needed to be done. While more than half of the colonies were made up of culturally aligned Anglophone Americans and Europeans, the Sinophone and Russophone colonies grew as well. Some of the colonies maintained contact with others, while others grew more insular and less likely to interact with others. All of them, due to strong founder population forces grew to be culturally monolithic, and the possibility for the boil off effect; those who didn't fit into the society could go found small little Utopian communities, or do whatever they wanted to, on their own.
2511 A.D. First contact with a non-Earth alien; a human of the Altairan variety. By now, the post-Terran colonials have multiplied into being nearly a billion strong across nearly a dozen worlds, but this is a major sea-change in their perception. The Terran colonists start to pull together and organize themselves into Federations and Confederacies, paving the way towards the eventual organization into pseudo-Imperial coalitions that evolve by 3000 A.D. The genetic similarities between the Terrans and the Altairans led to the origin of the Gray Hypothesis. Indeed, as ruins found on Altair's moons supplemented and bolstered this theory, purporting to be ruins of Grays themselves sent to monitor the Altairans, presumably after their relocation from Earth to Altair.
2564 A.D. The first discovery of non-human aliens, the humanoid Hulks. Within the next three centuries several more non-human species are encountered. To date; no first contacts are with interstellar societies.
2628 A.D. Contact with the Ubrai Empire, the first truly interstellar society other than that of the expatriate Earthmen. Although exotic, with a gracile build, a pale white skin tinted with blue, and wispy hair the color of wheat, the Ubrai are obviously human.
2669 A.D. The first Ubrai-Federation War starts. Due to logistical challenges with regard to space travel, the war lasts for more than fifty years, although it is only "hot" on occasion.
2701 A.D. An anonymous Ubrai scientist, experimenting with the concepts of the bulk drives ability to pierce the known universe/brane to try and develop a weapon for use in the war, accidentally creates an energy wave emanating from the bulk. Although exactly what happened is still very unclear, either some kind of parasitic element came from the bulk, or some existing element was mutated and corrupted by the energy leaking from the bulk. Taskin, the world on which this happened was completely depopulated due to plague, and declared a permanent quarantine world. The plague spread from there, although weaker, and eventually affected nearly all of the Known Sectors. Population fell across the entire area by as much as 50%. The war came to an end as everyone hunkered down and focused on local affairs. The centralized governments almost completely disappeared.
c. 2850 A.D. After several generations, interstellar travel and expansion was able to start back up again, as population booms following the plague affected many worlds. One interesting side effect of the plague is that through a combination of anti-bodies and symbiosis between the extra-dimensional virus and the people who managed to survive the plague as carriers is that small changes to the genetic code of a handful of people, relatively speaking. Those affected by this change have the genetic predisposition to access energy from the bulk.
c. 2925 A.D. The first traditions of using psionic energy; this energy from the bulk, become established. These are the very early Psionic Knights.
2945 A.D. The second Ubrai-Federation War. The end result, after several years of conflict is a new polity that incorporates citizens of both as the Interstellar Republic.
c. 3000 A.D. While the exact date is uncertain, around here there was a tipping point where the Republic as an actual republic that cared about the will of the people became a Potemkin Republic that was an actual Empire, although not one in name. It wasn't until nearly 3100 A.D. that it openly embraced it's identity, when the Chancellor officially declared himself Emperor.
3009 A.D. Contact with the growing alien-human Idachar civilization. Within a few years, a long-term Cold War starts which lasts for centuries.
c. 3100 A.D. A violent order of psionic Knights with a zealous Manifest Destiny doctrine attempts a coup of the government. Although defeated, they do a significant amount of damage to the Empire, then flee to uncharted space, where they establish the Shadow Empire.
3387 A.D. After many centuries of cosmopolitanism between the various ethnicities, the Empire is no longer heavily populated by any one single population core (although various regions within it are.) The government, in a need to maintain control, has gradually eroded much of the freedoms that its citizens once enjoyed. Resistance and rebellions have been inevitable for years, but in this year, open rebellion starting in the New Texas system.
3407 A.D. The Shadow Empire and its Rampage Knights invade the Interstellar Empire during its ongoing civil war. This state of near constant war persists for centuries. At the end of it, vast populations have been wiped out and/or displaced, and the demographics of many systems across the Known Sectors are changed. The Interstellar Empire has been overthrown, and in its place are two new polities; the Interstellar Republic (2.0) and the Monarchy. The Shadow Empire has also expanded into many areas that were formally part of the Interstellar Empire.
3766 A.D. The current King of the Monarchy calls a Crusade against the Republic to free its capital. Both polities claim the mantle of heir of the old Empire, and the bitterness of the Monarchy that the former capital belongs to the Republic is deep. The Republic is almost completely overthrown, and the Capital world is in possessed by the Monarchy for more than twenty years.
3811 A.D. After decades of war, many groups have formed splinter states of much smaller size than the traditional Empires or mega-state polities. This is especially common on the "frontiers" but sometimes even in the geographical center of the Known Sectors. The Republic, after retaking the Capital and a few other worlds, officially embraces a Revanchist policy and becomes the Revanchist Republic.
3984 A.D. The present day.