November 19, 1863.

With the exception of the Declaration of Independence, the Gettysburg Address has done more than any other document in American history to shape the ideals which define our nation. In fact, it’s the synthesis of the two documents that helped create the American we know today – an America that didn’t exist before Lincoln’s famous speech. Understanding the importance of Lincoln’s brief address on this – the 150th anniversary – sheds light on our origins as a nation, our national struggles today, and the role of the Gettysburg Address as bridge between the two.

The Gettysburg Address was born in the collapse of the United States. When the Southern states seceded from the Union in late 1860, they did so citing much of the same rhetoric Jefferson used to justify American independence from England. The South even went so far as to draft its own Declaration of Independence, copying much of the language from the original.

This put President Lincoln in a bind. It was hard to argue with Southerners on the independence question when they were espousing the Declaration and claiming to be the second American Revolution. Lincoln could hardly argue that Jefferson was wrong, that the Declaration was of no real value, or that men did not have a right to self-determination.

The part of the Declaration that most of us know, that our third grade teachers made us memorize, is actually the second paragraph of the Declaration. It’s the part that begins “We hold these truths to be self-evident.” There is, however, an entire paragraph before this section that is largely ignored today. Prior to the Civil War, this paragraph was for most readers the heart of the Declaration.

The first paragraph of the Declaration is a statement of revolutionary principles. It frames the rest of the document. When read in this context it becomes clear that the Declaration is exactly what Jefferson meant it to be – a justification for one group of people to break off from another to form their own country. That’s how the Declaration was read prior to Lincoln’s famous address.

All this changed on November 19, 1863, during the middle of our Civil War. Edward Everett had been invited to speak on the field of a terrible battle that had occurred just a few months before. Everett was one of the most famous politicians of the day, and a noted orator who promised to give an emotional and patriotic two-hour speech. The field was in a little town called Gettysburg.

Several thousand soldiers had been killed during three days of fierce fighting near the town. Burial of the dead was made almost impossible by the summer heat, foul stench, and overpowering flies from the decomposing bodies. The townspeople turned the field into a mass grave. It was this burial field that Everett had been invited to dedicate. As an afterthought, someone invited the President of the United States to say a few remarks as well.

After Everett delivered his oration, Lincoln stepped up on the podium and pulled from his breast pocket a piece of paper. It was a speech rumored to have been written largely on the train from Washington to Pennsylvania. In reality, Lincoln had agonized and labored over the speech far in advance. At only 272 words, Lincolns address was substantially shorter than the first speaker’s.

Four score and seven years ago our fathers brought forth on this continent a new nation, conceived in Liberty, and dedicated to the proposition that all men are created equal.

With these opening words, Lincoln returned to the Revolution and reframed the Declaration of Independence. No longer was Jefferson’s document just about revolution and the rights of men to establish new governments. Lincoln created a new interpretation – that the Declaration of Independence was also about equality and the rights of man. In essence, he shifted the focus of the Declaration from the first paragraph to the second.

Now we are engaged in a great civil war, testing whether that nation, or any nation so conceived and so dedicated, can long endure. We are met on a great battle-field of that war. We have come to dedicate a portion of that field, as a final resting place for those who here gave their lives that that nation might live. It is altogether fitting and proper that we should do this.

Lincoln knew was he was doing. By emphasizing the second paragraph of the Declaration, Lincoln changed the focus of the War Between the States. The war was no longer about revolutionary principles and Southern Independence. It was now a war for the equality of man and an end to the abysmal institution of slavery. It was a moral crusade to uphold the vision of the Founding Fathers and prove that democracy was a viable form of government. In short, it was a battle of the people, by the people, and for the people.

But, in a larger sense, we cannot dedicate — we cannot consecrate — we cannot hallow — this ground. The brave men, living and dead, who struggled here, have consecrated it, far above our poor power to add or detract. The world will little note, nor long remember what we say here, but it can never forget what they did here. It is for us the living, rather, to be dedicated here to the unfinished work which they who fought here have thus far so nobly advanced. It is rather for us to be here dedicated to the great task remaining before us — that from these honored dead we take increased devotion to that cause for which they gave the last full measure of devotion — that we here highly resolve that these dead shall not have died in vain — that this nation, under God, shall have a new birth of freedom — and that government of the people, by the people, for the people, shall not perish from the earth.

When Lincoln’s remarks were over, the crowds were largely unmoved. They had been expecting a longer oration and gave Lincoln low marks for his presentation. Only Edward Everett realized the significance of what Lincoln had done. Lincoln had reclaimed the Declaration of Independence from the South and reframed it. By doing so, Lincoln deprived the Southerners of their moral claims to an independent South, and turned the war into a morality play. Everett later told Lincoln, “You said in two minutes, what I tried to say in two hours.”

Lincoln’s address did more than just commemorate a battle that would become the stuff of legend. The Gettysburg Address placed the notion of Equality on par with the Founder’s emphasis on Liberty. In essence, it reinvented the nation. This is what Lincoln meant when he spoke of a “new birth of freedom.” What we see today in the political arena is the expression of these now equivalent goals, with one party defending Liberty and another championing Equality. The lasting legacy of Lincoln’s brief speech 150 years ago today is that it changed the way we read the Declaration of Independence, the purpose of American politics, and what it means to be an American.

Dr. Hammons is the Dean of the School of Humanities and a professor of Government at Houston Baptist University. He teaches classes on the American Founding and Constitutionalism. A version of this essay was previously published in the Houston Chronicle on November 17, 2013.