Civil liberties are a thing the Founding Fathers of the United States of America developed into an important part of how the USA is governed and a primary reason liberals like that Country. Civil liberties are also important in other liberal Democracies.
The Founding Fathers of the United States of America didn't actually create Civil rights. They may have been the first modern men to write the idea of universal civil rights into law, but they developed the idea in concert with others of the Enlightenment, and would probably tell us they recognized those rights rather than creating them. In fact, they insisted that those rights were innate and/or God given.
Not all the Founding Fathers were enlightened Liberals, but the Founding Fathers were some of the wisest and best educated of the new country, so there were plenty of them that were Liberals. Some were more enlightened Liberals, and those enlightened Liberals greatly influenced the foundation of government. However, even most of the enlightened Liberals of the time recognized that it would take time and education to create a Liberally enlightened culture, society, and government.
Much of American history is the conflict between those who want immediate extension of rights, those who fear immediate extension of rights, and those who wish to stop or reverse the extension of those rights. We're Liberals, so we want to enlighten our people and cultures, but we recognize that these things have to progress. Radicals tend to wish immediate change, and the histories of radical movements are often written in blood. On the other side of the spectrum are the arch conservatives who wish to limit civil rights and rely instead on traditional privilege, and their history is one of fear and repression and more blood.