WASHINGTON -- Before a crowd of more than a million, Barack Hussein Obama claimed his place in history as America's first black president, summoning a nation to unite in hope against the "gathering clouds and raging storms" of war and economic woe.

People of all colors and ages waited for hours Tuesday in frigid temperatures to witness the moment as a young black man took command of a nation founded by slaveholders. It was a scene watched in fascination by many millions around the world.

"We gather because we have chosen hope over fear, unity of purpose over conflict and discord," the nation's 44th president said.

The presidency passed to Democrat Obama from Republican George W. Bush at the stroke of noon, marking one of democracy's greatest gifts: the peaceful transfer of power.

But it was a stark transfer all the same. In one of the new administration's first acts, Obama ordered federal agencies to halt all pending regulations until further review -- this after Bush's final weeks raised debate over rushing new rules into effect on the way out the door.

Obama plunges into his new job in earnest today, meeting with his economic team and Iraq advisers while Congress gives his economic revival plan a going-over and takes up the nomination of Hillary Rodham Clinton to be secretary of state.

On the Capitol steps, he placed his left hand on the Bible used by Abraham Lincoln and repeated the inaugural oath "to preserve, protect and defend" the Constitution. A cheer went up.

"What is required of us now is a new era of responsibility -- a recognition, on the part of every American, that we have duties to ourselves, our nation, and the world, duties that we do not grudgingly accept but rather seize gladly," Obama said. "This is the price and the promise of citizenship."

Obama wove a thread of personal responsibility and accountability through his 18-minute inaugural address. A liberal Democrat proposing billions of dollars in new spending, Obama nonetheless spoke of the limits of government.

"It is the kindness to take in a stranger when the levees break, the selflessness of workers who would rather cut their hours than see a friend lose their job which sees us through our darkest hours," he said. "It is the firefighter's courage to storm a stairway filled with smoke, but also a parent's willingness to nurture a child, that finally decides our fate."

Obama's 10-year-old daughter, Malia, aimed a camera at her father as he spoke.

"Starting today, we must pick ourselves up, dust ourselves off and begin again the work of remaking America," Obama said.

He alluded to the inability -- or unwillingness -- of Americans to adjust to the passing of an industrial-based economy. "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. With that, the 47-year-old former Illinois senator transformed himself from a candidate claiming his campaign is about the voters to a president promising to put the nation in the people's hands.

Unlike most predecessors, Obama takes office with his agenda in many ways set for him.

An economy that seems more foreboding than at any inauguration since Franklin D. Roosevelt took office in 1933, with some 11 million people now out of work, and trillions of dollars of stock market investments lost. Two wars, one in Iraq that most of the country has long wanted over and another in Afghanistan that is spiraling downward and needs an overhaul. The continuing fear that another terrorist attack is not out of the question.

Obama's inaugural address only glancingly mentioned a series of promises from his campaign: to get the U.S. out of Iraq, stabilize Afghanistan, create jobs, "restore science to its rightful place," boost the use of alternative energy, address climate change, transform schools, manage government spending wisely and oversee a more bipartisan, less-divisive approach to policy-making.

To a world eager for his leadership to replace Bush's, Obama had welcome words: "We are ready to lead once more."

His ascension to the White House was cheered around the world as a sign that America will be more embracing, more open to change. "To the Muslim world," Obama said, "we seek a new way forward, based on mutual interest and mutual respect."

Still, he bluntly warned, "To those leaders around the globe who seek to sow conflict, or blame their society's ills on the West -- know that your people will judge you on what you can build, not what you destroy."

The day began well before dawn as people made their way downtown to secure spots from which to witness history, and it was extending well past midnight through a swirl of 10 official inaugural balls and many more unofficial galas.

The drama exceeded even the breathless buildup of recent days' nearly nonstop discussion on TV, blogs, podcasts and text messages. Not only heavily policed and barricaded Washington but much of the country virtually halted in its tracks -- even, albeit briefly, inside the casinos of Las Vegas.

The nation has celebrated 55 inaugurations, but none like the one that made a president out of the son of Kenya and Kansas, a man who rose to America's highest office largely untested at executive leadership, his political experience encompassing only four years in the U.S. Senate and eight in the state legislature of his home state of Illinois.

Blacks especially powered the jubilation that was thick in the chilly air. Even though Obama didn't give the topic of race, his or others, much treatment in either his campaign nor his inaugural, blacks poured into Washington from all over to watch firsthand as one of their own at last shattered a painful racial barrier.

"It almost leaves me speechless," said 69-year-old Tony Avelino, who traveled from Brea, Calif. "This situation is so emotional it's basically an unreal experience," added 56-year-old Cleveland Wesley, on the Mall from Houston with his wife as the sun rose.

Many others also see in Obama fresh reason for optimism at a time of great national insecurity. Or a chance for rest from the eight acrimonious years of the Bush presidency. Or even a turn toward modernity, as a country hurtling into new ways of communicating, connecting and conducting business chose a man more comfortable in that world than any leader before him.

Excitement over Obama's young, camera-ready family and the thought of Malia Obama and her sister, 7-year-old Sasha, turning the stately White House into a children's playroom also figured prominently in the day.

In a country nearly evenly divided between Democrats and Republicans, protests were nearly unseen, a shift from the two Bush inaugurations that were marked by boisterous demonstrations. One group of about 20 people from a Baptist church in Kansas demonstrated with anti-gay slogans.