At its simplest, the national symbol of the Jeffersonian Republic is a white, five-pointed star on black, symbolizing a united Republic across the depths of space; you will see this symbol repeated in various forms on most of these flags. Several old Terran flags have been adapted to Jeffersonian use by replacing some or all of their original blue with the black of space. 
This, then, is the National flag of the Jeffersonian Republic, adapted from the First National Flag of the Confederate States of America, the "Stars and Bars."
The Jeffersonian Republic is a society of contradictions. Individual liberty is valued above all things, yet at any time at least forty percent of the population has served or is serving in what can be considered the military. The Confederate States of America and their struggle for states' rights and independence from northern federalism are revered, yet Jeffersonians revile the ancient forms of discrimination and consider themselves a single, united society; indeed, though the Republic now consists of over twenty inhabited planets, moons, stations and other outposts, many of them rich in unique cultures, the national flag - adapted from the first national flag of the Confederacy - continues to bear a single star. Roles which Terran societies have long thought the traditional business of government, such as health care and education, are filled by a plethora of corporations, charities, and other private concerns, which compete in a free-market system to woo customers, instead of forcing people into de facto government monopolies. The mere suggestion of government intervention in free-enterprise, or in day-to-day business or private life, is sufficient to end political careers (or, in at least one famous case on New Texas early in Republic history, risk summary execution by enraged Citizens). Perhaps the greatest contradiction for a non-Jeffersonian mind is the fact that, although the Republic is the most heavily-armed society in Human history, with military weapons commonly in the hands of ordinary civilians and even some interstellar warships privately owned, violent crime is almost nonexistent throughout Republic worlds, and most other forms of crime are rarer than in any other modern society.
Most of the Founders of the Republic were formerly citizens of the United States of America, and most of these in turn were from the rural Western, or former-Confederate Southern, states, and this is reflected in the Republic's dialect, commonly called the American language, flavored with accents and slang from what was known as "flyover" country in the last Terran republic. Depending on who utters it, and in whose company, the term "redneck" can be a high compliment or a grave insult. Despite what urban Terrans might imagine on hearing a Jeffersonian speak, the standard of living and average education of the typical Jeffersonian Citizen is far higher, by any objective measure, than any other society in history, even that of the United States.
There is a proverb common throughout the Republic, spoken by Jeffersonians to Terrans or other foreigners who express confusion at these apparent contradictions: "It works for us, you must not be doing it right." Other societies, particularly Terran, often accuse Jeffersonians of arrogance, but the accusation falls flat in the face of Jeffersonian performance in the Republic-Empire War, treatment of the Eyani people, ongoing scientific and technological growth, and the incomparable and constantly-growing wealth of this interstellar nation. Not since the United States of America, on pre-starflight Terra, has a single nation been so vastly and demonstrably superior to all others.
