RAY SUAREZ:New Year's Day marks the 150th anniversary of the Emancipation Proclamation, and the National Archives in Washington, D.C., honors the occasion with a rare public viewing.

It's one of the defining documents of American democracy, issued on Jan. 1, 1863 by President Abraham Lincoln. The Emancipation Proclamation declared that: "All persons hell as slaves within any state or designated part of the state in rebellion against the United States are and hence forward shall be free."

Those words marked a turning point in the Civil War, staking a moral dimension to the Union cause. And the document became a symbol of hope for the nearly four million slaves held in Confederate states.

Reginald Washington is a senior archivist for the National Archives.

REGINALD WASHINGTON,National Archives: It confirmed their belief that the war should always have been a war for -- not to preserve the Union, but a war to free the slaves.

HARI SREENIVASAN:Written on paper, rather than more durable parchment, the Proclamation has faded over the years from light exposure, and now spends most of the time in protective dark storage in the National Archives.

But it commands large crowds on those rare occasions, like today, when it's on public display. And even 150 years later, it retains the power to inspire.

SONDRA SHOOT,Washington, D.C.: It's a historical document. It's something that I think is important to our country, our nation and specifically African-Americans.

JOANNE BUTLER,Washington, D.C.: This is the document really that started it all to free the black slaves, so I had to come see it.

HARVEYBUNCH,Washington, D.C.: Had to come down after researching my great-grandparents, all of whom were slaves. And so I had to come and see that document.

LYNDA BAER,Washington, D.C.: And it's such a mixed—it's such a mixed group, old, young, black, white, brown, red, men, women, children, absolutely fantastic.

HARI SREENIVASAN:The Emancipation Proclamation remains on view to the public through 5:00 p.m. New Year's Day.

For more on the history and significance of the Emancipation Proclamation, we turn to Annette Gordon-Reed, professor of history and law at HarvardLawSchool. She won the 2009 Pulitzer Prize in history for her book "The Hemingses of Monticello: An American Family."

Professor Reed, we just saw a long line snaking around the National Archives. The event is one thing. How come an object has that kind of power, do you think?

ANNETTE GORDON-REED, Pulitzer Prize Winner: Well, it's an iconic document in American history.

And Americans like to look at things like that to remind us the sort of journey that we have been on from the beginning of the country's foundation. The Declaration of Independence, the Emancipation Proclamation, these are the things that are sort of the touchstones for where we have been and where we hope we are going.

RAY SUAREZ:I have seen people waiting hour to see, in effect, words.

If you go to ancient cathedrals in Europe, let's say, they may wait in long lines to see objects that connect to saints, kings and queens. Are we a republic of words? Are they so important that we will wait a long time to see them?

ANNETTE GORDON-REED:Well, people have said that America is a country that is founded upon ideals and ideas that are expressed in words. And so it makes sense that people would look at these words, as I said, to try to tell us who we are and the kinds of things that we hope to be. So, yes, words mean a great deal to Americans and always have.

RAY SUAREZ:Looking back at the Proclamation itself, as a practical matter, what did that declaration do for people still in bondage in the Confederacy?

ANNETTE GORDON-REED:Well, it reconfirmed their idea that the war was about the end of slavery.

And, in fact, upon hearing these words and understanding that the Proclamation had been made, thousands of African-Americans left plantations. They voted with their feet, so to speak, to say that this was going to be a new day.

So the Proclamation gave them hope that this—all of their hopes were going to be realized. And so it really did put a lot of people in motion during that time period.

It didn't free the slaves, obviously. The Confederates and the people who were in control of them remained in control until the end of the war. But blacks took a part in liberating themselves upon hearing the words of the Proclamation.

RAY SUAREZ:How did word get around? How would an enslaved person working on a plantation in Alabama, working in a factory in Virginia even know that this had happened?

ANNETTE GORDON-REED:Well, there wasn't much that was going on in society that enslaved people didn't know about, because they lived cheek by jowl with whites, who talked about this sort of thing. And slaves traveled around. They ran errands. They went from plantation to plantation, word of mouth.

John Adams, in colonial times, mentioned the sort of incredible intelligence network that African-Americans seemed to have, the grapevine that carried news from far and wide in the plantations, plantations south. And it actually operated as well during this time period.

So, from hearing about things, carrying the word forth, they definitely knew about it.

RAY SUAREZ:One thing the Emancipation Proclamation didn't do was free enslaved people legally owned in the United States, in Kentucky, in Maryland, in West Virginia.

Did the owners in those places know that the institution's days were numbered, even though they were still part of the Union?

ANNETTE GORDON-REED:Well, they certainly feared it.

Southerners in the Deep South and in the border states understood that when Lincoln and the Republicans moved to stop the halt of slavery, the expansion of slavery, in a way, it was sort of the death knell of slavery. Slavery was an expansionist institution.

So to say that you were going to leave slavery in place in the places where it was, was another way of saying that it could no grow. And if it could not grow, it would die.

So I think lots of people understood what the story was. But not freeing the slaves in the border states was a—was—excuse me—a political calculation on Lincoln's part. And he was a great politician, after all.

RAY SUAREZ:So, all that remained to be done was to negotiate the terms?

I mean, the president of the United States at that time in the 19th century wasn't thought to be able to tell property owners that their property wasn't theirs anymore.

ANNETTE GORDON-REED:But with the war—the war changed all of that. And he took measures as a commander in chief that he thought were necessary in order to facilitate the winning of the war.

And it was pretty clear by this time what was going to happen. Things had been put in motion.

As I said, African-Americans were in motion, flooding Washington, other points in the North, escaping slavery. So I think the die had been cast and people understood that.

RAY SUAREZ:We heard somebody rhapsodizing about the line there, and seeing who was waiting in line, a little bit of everybody.

It has been 150 years. The country has changed a lot during that time. And tens of millions of Americans are not descended from people who were even living in the United States at that time. Is the Emancipation Proclamation still, for all that, part of our common patrimony? Is it ours even if we just got here the day before yesterday?

ANNETTE GORDON-REED:Oh, it absolutely is.

The Declaration is our patrimony. The Constitution is our patrimony and the Emancipation Proclamation as well. When you come to a country, you come and you take the bitter with the sweet, the good and the bad. All parts of American history belong to all Americans today.

So it goes together. All these things are part of who we are. And I think that Americans, whether you recently arrived here or you have been here from the 1700s, or the 1600s, as most African-Americans have been, it is a part of who we are and it is a part of our national patrimony.

RAY SUAREZ:Do you believe, as somebody who has grown up in this country, as someone who studied that period of our history very closely, that more Americans believe that, that we really are one people, that something like the Civil War and its events do belong to all of us?

ANNETTE GORDON-REED:Well, I think—I like to hope that people see it that way. As a historian, of course, I want everybody to be as excited about history as I am.

But I get the idea that people, people understand it. I mean, history is a popular subject for adults. It's not some for children, who feel that, you know, they don't want to memorize dates and so forth. But I do think that people are coming to understand that we have to know where we have been if we want to go know where we are going.

And I think the sort of long line suggests that this is something, a part of our understanding of who we are. Yes, so I hope so. That is my hope as an historian, at least.

RAY SUAREZ:Annette Gordon-Reed, professor, thanks a lot.

ANNETTE GORDON-REED:Thank you for having me.

JUDY WOODRUFF:No matter what your age, you can read the Emancipation Proclamation on our website.