President Barack Obama has begun his second term by declaring that the nation's "possibilities are limitless."
Speaking before a flag-waving crowd of hundreds of thousands on the National Mall, Obama said a decade of war is ending, and the nation's economy is recovering.
Moments after taking the oath of office on a crisp day in the nation's capital, Obama said, "We are made for this moment, and we will seize it, so long as we seize it together."
In his second inaugural address, Obama didn't dwell on any first-term accomplishments, but instead looked to hard work ahead in a country still grappling with a sluggish economy. And he urged Washington to find common ground over his next four years.
He rejected the idea that the nation "must choose between caring for the generation that built this country and investing in the generation that will build its future."
He also said the nation must "respond to the threat of climate change" and tackle the issue of immigration reform. And he said it must protect its children from the kind of violence that erupted in a Newtown, Conn., elementary school.
Obama earlier placed his hand on two Bibles -- one that was used by Martin Luther King and the other used by Abraham Lincoln -- and recited the oath of office.
Vice President Joe Biden was also sworn in for his second term.
Earlier, President Obama said "we must act" even if our work is imperfect. He said we cannot afford to delay.
In a message that could be aimed at the divided Congress where battles await him in his second term, Obama cautioned against mistaking absolutism for principle, substituting spectacle for politics or treating "name-calling as reasoned debate."
Even so, Obama says that today's accomplishments will be partial, and it will be up to people four, 40 or even 400 years from now to advance them further.
The president spoke at the U.S. Capitol after taking his public oath of office for his second term.
After his speech, Obama is expected to dine with members of Congress and other VIPs at a Capitol Hill luncheon. He will then view the traditional inaugural parade and is scheduled to attend two inaugural balls on Monday night. (AP)
U.S. Senator Dean Heller (R-NV) issued the following statement:
"Today I join Americans across the country by gathering to witness the Inauguration ceremonies of the President and Vice President of the United States. On this day, we celebrate the strength of our democracy and recognize that Americans across the political spectrum stand united behind the ideals outlined in our Constitution.
"As President Obama puts forward his vision for the next four years, we also pay tribute to the vision and life of Dr. Martin Luther King Jr. Not only do we recognize Dr. King for his service, but we also remember him as both an inspirational leader and advocate of tolerance, peace, and equality. His vision for America stands as an example for us all and I join with everyone across this great nation in honoring his legacy," said Senator Dean Heller.
Even though President Obama's second inaugural again drew huge crowds to the National Mall, people who were there for both events say this one doesn't quite compare.
Sharon Davis of Maryland says there was "a lot of energy" today -- but that last time "it was just off the charts."
Today's festive crowd of flag-wavers filled the Mall to overflowing, and cheered Obama's swearing-in and his 18-minute inaugural address -- about the same length as his address four years ago.
Skies today were overcast with a breeze, and the temperature was 40 degrees at noon -- sparing the crowd the biting cold morning of four years ago.
Metro officials said subway trains through downtown Washington this morning were no more crowded than they would be on a typical workday. The government is closed for the Martin Luther King holiday -- so the usual commuters were replaced by crowds headed to the inauguration.
One couple from South Carolina took a leisurely ride from their downtown hotel to Union Station. Four years ago, they had to walk across a bridge over the Potomac River. Terry Alexander says, "It was crazy. This is calm."
Meanwhile, authorities in Washington reported no major problems with security or crowd control, before or during today's inauguration ceremony at the U.S. Capitol.
Police have been stationed in rail stations and on street corners. National Guard Humvees are blocking some intersections downtown. And spectators have shuffled through security checkpoints to be screened for prohibited items, including balloons and glass containers.
Flight restrictions were in place in the skies above Washington.
Even though the crowds this year haven't matched the record-breaking turnout of four years ago, there have been sporadic reports of slow-moving security lines. A checkpoint between Union Station and the U.S. Capitol came to a halt so a motorcade could pass and barriers could be repositioned. Stuck spectators vented on Twitter that the line didn't move for at least a half hour.
Still, many of those who were there four years ago said this year was a lot easier.
A smattering of protest groups occupied spots along the parade route -- but the demonstrations were largely directed at long-running national and international concerns, rather than policies specific to the Obama administration. A few dozen protesters with a social justice coalition gathered near the White House to honor Martin Luther King's legacy and call for jobs, not war.
An inauguration planning official says turnout was "definitely above 800,000" and possibly up to one million people.
Chris Geldart, who directs the District of Columbia's homeland security and emergency management agency, says early and unofficial estimates of the number of people on the National Mall indicate a turnout higher than 800,000. That's based on aerial views of how the crowd filled sections of the mall.
Officials initially anticipated as many as 800,000 visitors, but lowered the projections to 500,000 to 700,000, based partly on an updated number of charter buses and restaurant and hotel reservations.
But Geldart, who's also co-chairman of the district's presidential inaugural committee, said the event benefited from relatively mild weather.=
About 1.8 million people attended President Barack Obama's first swearing-in in 2009. (AP)