People began gathering before dawn on the National Mall in Washington, D.C. By 7 a.m. crowds were packed in from the Capitol to the Washington Monument. Many walked for miles in the bitter cold, and others drove hundreds of miles.
By 9 a.m., nearly 410,000 people had ridden Washington's Metro train system, according to a Metro spokeswoman. The National Park Service also announced that due to the already overwhelming crowd size, it would close down a large portion of the National Mall. The National Park Service was instead redirecting people to the Washington Monument grounds.
Some recognizable names were among the sea of faces.
"We had to do a little walking, but it's nothing compared to many years, hundreds of years, that it took to get to this point in history for this country," director Spike Lee told ABC News' Robin Roberts.
"It's a lot of emotions really, because, I never thought it would happen either," said Magic Johnson.
"I am full of hope," said actor Denzel Washington. "You know, I feel that we can only go up from here. United. If we're all together, if we work together and respect our civic duty."
Just before Obama stepped up for the swearing in, pastor Rick Warren reflected on the moment in his invocation.
"We celebrate a hinge-point of history with the inauguration of our first African-American president of the United States," Warren said. "We are so grateful to live in this land, a land of unequaled possibility, where the son of an African immigrant can rise to the highest level of our leadership."
Pundits were quick to reflect on the president's words as soon as his speech was over.
"I think Obama was very careful in his speech today not to step forward and say, 'We're breaking with the past, we're starting everything fresh, here's how we're gonna do it,'" said Columbia University lecturer Joe Cutbirth. "I think it was much more sublime than that. I think he came out and said there are 44 people who have taken this oath and then he kind of talked, I felt like, as a continuation of the best part of our history. And it seemed to me like that was the frame for the speech."
"I think what he is saying to this country is, 'It's time to stand up and pull together and work," said Politico senior editor Beth Frerking. "That to me was the takeaway message of this speech."
During the Martin Luther King Jr. holiday weekend, more than 1 million people who traveled to the nation's capital and countless others who remained in their hometowns were similarly abuzz about the shift in Washington, D.C.
In the lead up to Inauguration Day, leaders in predominately black communities talked about their hopes for the future. Some recalled memories from decades ago when they attended Martin Luther King, Jr.'s March on Washington. Young students weighed in on how they'll overcome obstacles to realize their dreams.