That the election of Barack Obama as the United States' first African-American president was historic is an understatement. But perhaps lost in the excitement and emotion of Obama's victory speech Tuesday was just how truly American it was. Weaving into his address the words of Abraham Lincoln and Martin Luther King Jr., Obama tapped into the noblest tradition of American national unity. And in so doing, President-elect Obama traced the historical arc of the United States as a work in progress, a nation trying to fulfill its goal of becoming a more perfect union.

To be sure, in Chicago Barack Obama turned to the 16th president to offer an olive branch to the Republican Party he vanquished on November 4th:

"Let's remember that it was a man from this state who first carried the banner of the Republican Party to the White House -- a party founded on the values of self-reliance and individual liberty and national unity. Those are values we all share. And while the Democratic Party has won a great victory tonight, we do so with a measure of humility and determination to heal the divides that have held back our progress."

But Obama wasn't content to end there. Acknowledging the gravity of the political schism gripping the United States, Obama recalled Lincoln's plea from his First Inaugural:

"As Lincoln said to a nation far more divided than ours, 'We are not enemies, but friends -- though passion may have strained it must not break our bonds of affection.' And to those Americans whose support I have yet to earn, I may not have won your vote tonight, but I hear your voices, I need your help, and I will be your president too."

Lincoln's words, coming just weeks before the outbreak of the Civil War in 1861, stand among the purest expressions of national unity in the American canon:

"We are not enemies, but friends. We must not be enemies. Though passion may have strained it must not break our bonds of affection. The mystic chords of memory, stretching from every battlefield and patriot grave to every living heart and hearthstone all over this broad land, will yet swell the chorus of the Union, when again touched, as surely they will be, by the better angels of our nature."

As Obama suggested throughout his speech Tuesday, the partisan discord and political conflict he decries represent a threat to the very real work Americans together must do to ensure their "democracy, liberty, opportunity and unyielding hope." Facing two wars, an economic emergency and global energy and climate crises, Americans must be prepared to struggle and sacrifice to overcome:

"The road ahead will be long. Our climb will be steep. We may not get there in one year or even in one term, but America, I have never been more hopeful than I am tonight that we will get there. I promise you: We as a people will get there."

In preparing - in exhorting - Americans for the difficult times ahead, Obama echoed the civil rights icon Dr. Martin Luther King. Speaking to striking sanitation workers in Memphis the night before his assassination, Dr. King on April 3, 1968 hauntingly assured them of their ultimate triumph, one he might not live to share:

"We've got some difficult days ahead. But it doesn't matter with me now. Because I've been to the mountaintop. And I don't mind. Like anybody, I would like to live a long life. Longevity has its place. But I'm not concerned about that now. I just want to do God's will. And He's allowed me to go up to the mountain. And I've looked over. And I've seen the promised land. I may not get there with you. But I want you to know tonight, that we, as a people, will get to the promised land."

Speaking to 200,000 people in Chicago's Grant Park and to an audience of millions more worldwide, Barack Obama made clear that the American people - all of them - will get there.

With his address Tuesday, Barack Obama sought to extend the march of national unity and equality running from Lincoln through King and beyond. His ascendancy is not its culmination, but a step along the way. And to be sure, Obama stressed, the transformation of the United States into the "more perfected union" that 106 year-old Ann Nixon Cooper witnessed in her lifetime is far from finished:

"America, we have come so far. We have seen so much. But there's so much more to do. So tonight let us ask ourselves, if our children should live to see the next century, if my daughters should be so lucky to live as long as Ann Nixon Cooper, what change will they see? What progress will we have made?"

Just weeks before his own assassination in the waning days of the Civil War in 1865, Abraham Lincoln in his Second Inaugural issued the defining call for American national unity. "With malice toward none, with charity for all," the Great Emancipator said, "let us strive on to finish the work we are in, to bind up the nation's wounds...to do all which may achieve and cherish a just and lasting peace among ourselves and with all nations." 98 years later on the steps of the Lincoln Memorial, Martin Luther King told Americans, "I have a dream."

On Tuesday night in Chicago, Barack Obama reminded us that the dream - Lincoln's dream, King's dream, his dream - is ours. And in 2008, it is again time "to reclaim the American dream and reaffirm that fundamental truth that out of many, we are one."