(soft music) - [Narrator] Flags are clearly an important part of what it means to be an American.

But why is that?

Why do we care so much about a piece of cloth?

- Flags are like a human impulse.

There's no other way that we found to create a tangible or a visual artifact that could show emotions, that could depict how we feel and how we belong.

(engine roaring) And for Americans, flags are really about patriotism and pride.

(group cheering) - [Students] I pledge allegiance to the flag.

- [Neil] It's one small step for man, one giant leap for mankind.

- How many Supreme Court cases have there been about the model trains and how many soldiers have risked their lives with a battlefield for a stamp?

But flags have seen both of those things.

(soft music) - [Narrator] There are many extraordinary institutions in Washington.

One of my favorites is the Library of Congress.

- You're Mr. Rubenstein, aren't you?

- That's me.

- I retired from the library.

- Okay.

- The Library of Congress has grown to 170 million items, the world's largest library.

(soft music) It was modeled after an Italian palace to show that in this country, we built palaces to knowledge.

(upbeat music) This is the Gutenberg Bible, it is the earliest example of movable type.

And this particular copy is one of only three in the world.

- So this is about the most valuable book you can get, right?

- Oh yeah.

- [Narrator] Inside you can find answers to history's most important questions and maybe clues to understanding the Gadsden flag.

- This is the earliest print that we have here at the Library of Congress from 1779.

And as you can see, a rattlesnake is entwined and ready to bite the European powers.

- The rattlesnake or the serpent was about the most feared animal, I guess of the time.

That's why it was a symbol of.

- Well, Europe didn't have exotic venomous snakes like America and so it was feared.

(soft music) - Where are we now in the Library of Congress?

- Right now we're in the James Madison Memorial Building.

- [Narrator] So you have humidity control and other things here?

- Yes, it's a climate controlled vault and this is where all of our gold level collection items are stored.

We'll be having a look at this item.

- Okay, this is the Pennsylvania Gazette from 1754.

Join or die.

So this is the original Benjamin Franklin drawing?

- Yes.

- Of a serpent cut in pieces.

- Yes, so this was the first political cartoon published in America.

And what you'll see is all of these colonies are represented in eight pieces.

(upbeat music) - [Host] Rattlesnakes were these sort of defensive creatures by nature.

There was a certain appeal to that, this idea that we are gonna take the high ground, this defensive position, but if you mess with us, then we will come out fighting.

And so that passed this sort of colonial frontier, sort of rough around the edges, characteristic that many of these columnists saw themselves as possessing.