Many understand the historic significance of this Inauguration Day, but no one carries the burden more than Obama himself, who is now the first African-American president.
"There's no other country on Earth that can undergo these kinds of transformations with the same speed and yet still stay stable and still stay true to its core traditions," Obama told CBS Evening News anchor Katie Couric in an interview taped just days ago.
This day of great tradition began with one that was started by FDR in 1933, with the president-to-be attending church with his family.
After the service the president-elect and his wife Michelle arrived at the White House, greeted warmly by President Bush and wife Laura. It was a passing of the baton - the transition of power, democracy at its finest.
Then, Obama and the outgoing president
Starting before daybreak, people from around the country and around the world converged on the Mall to witness history.
Vice President Joe Biden was the first
The oath of office was followed by the president's.
There have been words in inaugural addresses that have been etched in our national memory, like FDR in 1933, telling the nation, "We have nothing to fear but fear itself."
Or John F. Kennedy, who said in 1961, "Ask not what your country can do for you - ask what you can do for your country."
Presidential historian Doug Wead says these tough times have put Obama in a position where Tuesday's speech had to be more serious than celebratory. "This was not a motivational speech this - was a come-to-work-speech," he said. "This was business. He's already started being president. He's working here. He was issuing instructions."
Obama's speech acknowledged the daunting challenges ahead. "That we are in the midst of crisis is now well understood. Our nation is at war, against a far-reaching network of violence and hatred. Our economy is badly weakened, a consequence of greed and irresponsibility on the part of some, but also our collective failure to make hard choices and prepare the nation for a new age," he said in his.
The new president also reached out. "To the Muslim world, we seek a new way forward, based on mutual interest and mutual respect."
But to the nation's enemies, he issued a warning. "For those who seek to advance their aims by inducing terror and slaughtering innocents, we say to you now that our spirit is stronger and cannot be broken; you cannot outlast us, and we will defeat you."
Aretha Franklin - one of the most beloved African-American singers of her generation and a symbol of black pride - performed "My Country, 'Tis Of Thee."
"I am playing a very small part in the swearing in, but I am just thrilled. And I'm over the top with it," she said.
She looks at this day as a culmination of the civil rights movement and the great men who paved the way for President Barack Obama. "I think he represents, yes, some of the fruition of the dream and the labor and the sweat and the blood and tears that went along with that struggle."
The San Francisco Boys and Girls Choirs were chosen to perform because they embody the American spirit and the promise of the future, among them Emma Ulriksen, 16, Duane Smith, 12, and Amelia de Snoo, 14.
"It's a really great feeling knowing that we're gonna be able to spread hope to this many people 'cause, like Obama, us as choristers, our goal is to spread hope to people listening to our singing, just as Obama spreads hope through his inspirational speeches," de Snoo said.
"Unlike adult choirs, we're younger and we represent the youth in America, which I think is important because the entire world is gonna be watching," she added.
Poet and friend of Obamaread a piece she called "praise song for the day."
And the Reverend Dr. Joseph Lowery, considered the dean of the civil rights movement, gave his benediction, ending it by saying "We ask you to help us work for that day when black will not be asked to get in back, when brown can stick around... When yellow will be mellow, when the red man can get ahead, man; and when white will embrace what is right. That all those who do justice and love mercy say Amen."
The crowd thundered, "Amen!"
After the ceremony, a reflective former President Bush said goodbye and headed home to Texas, the transition complete.
Then the Obamas took to the streets,
President Obama understands that his journey was more than a long shot - an African-American, a black father from Kenya, a white mother from Kansas.
"By all sensible odds, I shouldn't be sworn in as the 44th president. It was very unlikely, born to a single mom who was 18 at the time," he told Couric.
"If your mom could be here and could be standing near you as you're sworn in…," Couric asked.
"She'd be crying. She was a real softy," he replied.
Asked what he'd say to her, Obama said, "Thank you, 'cause me being here is a testimony to her love. It is a testament to just her fierce determination. So I'm a reflection of her. Wherever she is right now, I think she knows that."