It was a seemingly wistful moment at the halfway mark of his presidency, before the celebratory parade and the evening's galas.

Shortly after exhorting the United States to continue its "never-ending journey" to live up to the ideals of its founders, on his way off the platform at the West Front of the Capitol, President Barack Obama stopped to drink in the scene before him.

"I want to take a look one more time," he told those surrounding him. "I'm not going to see this again."

And so, with his oath of office taken -- again -- and the speech delivered, the president stood aside for 24 seconds on the chilly Monday afternoon, letting the crowd that had joined him for his formal, public second inauguration file past.

It was one of the few quiet moments on an otherwise jam-packed day. Obama stole another such moment with his wife, at the first of two official inaugural balls they were scheduled to attend Monday night.

Following performances by Alicia Keys, Brad Paisley and the Mexican rock group Mana, the first couple danced as Jennifer Hudson sang the classic song, "Let's Stay Together," by Al Green.

First lady Michelle Obama wore a floor-length, custom, ruby-colored chiffon and velvet gown designed by Jason Wu, the same designer behind her 2009 inaugural dress.

The celebrations came a day after Obama was sworn in on the constitutionally required date in a low-key ceremony at the White House. The flag-waving crowd that watched Monday's event was noticeably smaller than the throng that turned out for his first oath in 2009 but still packed the National Mall for blocks.

The waving flags, the red-white-and-blue bunting and the heralding trumpets marked the 57th such ceremony in the history of the nation, with the peaceful extension of power based on last November's election that returned Obama to the White House.

The Sousa marches, the ceremonial guns and the voices of James Taylor, Kelly Clarkson and Beyonce having faded away, Obama headed into the Capitol for a luncheon with members of Congress. Then he led the traditional parade up Pennsylvania Avenue, stopping near the White House to walk a few blocks of the route with the first lady to the cheers of those lining the sidewalks.

"You've got to come out for this," said Nick Pignone, a Washington resident. "Everyone's excited -- good vibes right now."

Also publicly sworn in for a second term was Vice President Joe Biden, who, like Obama, also took his official oath Sunday. Justice Sonia Sotomayor performed the honors for Biden at his home at the Naval Observatory in Washington, where the vice president's extended family and a few Cabinet officials gathered to watch the ceremony.

Biden and his wife, Jill, also took some time to walk part of the parade route, with a grinning Biden periodically jogging over to the sidelines to shake hands with people across the barricades. Once both couples and their families were seated at the White House reviewing stand, one of the first acts to pass was the marching band from Honolulu's Punahou School, Obama's alma mater.

What followed included dozens of military and school bands, Native American dance troupes whirling in traditional dress, war veterans, Civil War re-enactors, kilted firefighters blowing bagpipes and Montana's governor and congressional delegation on horseback and in cowboy hats.

Obama, the first African-American president and the 17th to win a second term, used a pair of Bibles in Monday's ceremony -- one from Abraham Lincoln, the other from Martin Luther King Jr. His roughly 2,000-word inaugural address hearkened back to both.

"I did everything possible today to keep from crying," said U.S. Rep. John Lewis, D-Georgia, a onetime lieutenant of King. He called the sight of Obama using King's Bible "very moving, unreal -- almost unbelievable."

Monday is also the federal holiday commemorating the birthday of King, who was assassinated in 1968.

The loudest cheer of Obama's address came when he said the nation's journey remained incomplete "until our wives, our mothers, and daughters can earn a living equal to their efforts," and "until our gay brothers and sisters are treated like anyone else under the law."

Obama begins the second half of his presidency with the opportunity to make it more historic but facing some of the same challenges that he struggled with in the first four years.

Americans "have the power to set this country's course," he said, urging people to fulfill their citizenship by meeting "the obligation to shape the debates of our time -- not only with the votes we cast, but with the voices we lift in defense of our most ancient values and enduring ideals."

On the Mall, Carlos Arieta and his wife, Sharon, took in the scene after driving from Atlanta to witness history. The former Washington residents said it was the first time they had attended an inauguration.

Surprised by the throngs gathered a few hours before the speech on a clear morning with temperatures just above freezing, Arieta said "it's nice to see all the different kinds of people."

Even some of those who didn't support Obama's November re-election turned out to watch. Don King, 27, and his 21-year-old brother Matthew said they don't agree with the president on taxation, debt and other fiscal issues but didn't want to miss this bit of history.

"It's the second inauguration for Obama, and it's pretty amazing if you think back to the 1800s and later during the civil rights era, that we're here," Don King said.

A new CNN/ORC International poll released Monday indicated less excitement this time than four years ago, when nearly 2 million people crowded the Mall despite frigid weather for Obama's historic first inauguration.