WASHINGTON -- Barack Hussein Obama became the 44th president of the United States on Tuesday, a confident young leader ushering in a new era with a promise of bold action to lift the country out of the worst economic crisis since the Great Depression.
Taking the oath on the steps of a Capitol built in part by slaves, Obama became the first African-American to reach the pinnacle of American political life, fulfilling at last the full promise of a nation born with the pledge that all men are created equal.
He looked out over a sea of perhaps 2 million people, faces of every color, creased with age and fresh with promise, celebrating a turning point of history and looking eagerly for a new voice and vision to lead the country in a new century.
"Today I say to you that the challenges we face are real. They are serious and they are many," he said in a 19-minute inaugural address that was at turns sober about the nation's problems and uplifting about its prospects. "They will not be met easily or in a short span of time. But know this, America: They will be met."
To his countrymen, he urged "a new era of responsibility," but also a greater role for the government, help for the poor and a stronger hand in regulating private markets, which, he said, "without a watchful eye ... can spin out of control."
To the world, he vowed to protect American security without violating "the rule of law and the rights of man," and to talk even to hostile nations. "We will extend a hand if you are willing to unclench your fist," he said.
To those who threaten the United States, he said, "you cannot outlast us, and we will defeat you."
The man he succeeded, George W. Bush, watched quietly from his seat, his time over and the legacy of the Bush era of 20 years in high office -- his eight years as president and his father's 12 as vice president and president -- now left to history.
The peaceful transfer of power was a majestic reminder of democracy at its finest, marking the public's wish to change course, from one political party to another, from one generation to another. At 47, Obama is the first American president who came of age after the turbulence and divisions of the 1960s and the Vietnam War.
Shortly after he became president at the stroke of noon, Obama placed his hand on the same Bible that Abraham Lincoln used at his 1861 inauguration and, following Chief Justice John G. Roberts, took the oath: "I, Barack Hussein Obama, do solemnly swear that I will execute the office of president of the United States faithfully, and will to the best of my ability preserve, protect and defend the Constitution of the United States."
Obama paused for a second when Roberts placed the word "faithfully" at the wrong spot in the sentence, then repeated it as Roberts had, not as it was written into the Constitution more than 200 years ago, which is "faithfully execute the office."
He finished with the phrase that George Washington added and every president since has used voluntarily: "So help me God."
His wife, Michelle, and his young daughters, Malia and Sasha, stood beside him, smiling broadly. Artillery hailed the man and the moment with a 21-gun salute that echoed through the marbled monuments.
Bush, 62, left office one of the least popular presidents of the last century, economic turmoil the punctuation mark on a disappointing presidency. Eleven million Americans are out of work, and more than $1 trillion in stock values has been wiped out.
Bush's dismal standing with the American people rivaled those of Harry S. Truman when he left office in 1953 and Richard Nixon when he resigned in disgrace in 1974.
Bush left Washington quickly, his helicopter flying past the White House one last time, then turning past the Lincoln Memorial toward Andrews Air Force Base in the Maryland suburbs.
He departed Andrews for Texas while Obama was still lunching in the Capitol. Bush flew aboard the familiar 747 jet, but found it stripped of the Air Force One radio call sign, which is used only when the president -- the current president -- is aboard.
The Capitol luncheon was disrupted when Sen. Edward Kennedy, D-Mass., who's battling a brain tumor, suffered a seizure. Obama rushed to the side of the Senate's "liberal lion," then spoke to the room after Kennedy was escorted out.
"Right now a part of me is with him," Obama said. "And I think that's true for all of us."
The ceremony was seen around the world, by American troops standing watch in such far-flung places as Afghanistan, Iraq and South Korea, and by countless citizens of other countries eager to see the new young president take power.
On his first full day in office Wednesday, Obama plans to attend a National Prayer Service, then meet at the White House with top military officials, including Defense Secretary Robert Gates; Joint Chiefs Chairman Adm. Michael Mullen; Army Gen. David Petraeus, the commander of the U.S. Central Command; and Army Gen. Ray Odierno, the commander of U.S. troops in Iraq.
Obama is expected to discuss the wars in Iraq and Afghanistan and the future of the detention center at Guantanamo Bay, Cuba. He's also expected to sign an executive order this week ordering the closure of the detention center. It could be months before the facility closes, however, as the administration determines where to put the remaining 250 detainees.
The new president acted almost immediately Tuesday to order all federal agencies to put a freeze on all pending regulations until his administration can review them. The order, contained in a memo signed by White House chief of staff Rahm Emanuel, isn't unusual, but the Bush administration approved a number of last-minute environmental and other federal regulations.
For most Americans, the inauguration was a moment for hope. For black Americans, it was something more, the culmination of a centuries-long wait to see the Founding Fathers' promise of equality fulfilled.
Among those attending were several of the nine African-Americans who, as children, needed the protection of National Guardsmen when they integrated Little Rock Central High School in 1957. Also among the honored guests were the surviving Tuskegee Airmen, the famed African-American aviators of World War II.
On the National Mall, children smiled and waved flags. Older Americans with memories of past struggles wiped tears from their eyes.
They stretched shoulder to shoulder for the two miles that separate the Capitol from the Lincoln Memorial, where the Rev. Martin Luther King Jr. once spoke of the "dream" of such a moment when Americans would be judged by the content of their characters and not the color of their skin.
"We rejoice not only in America's peaceful transfer of power for the 44th time," said Rick Warren, a California pastor and writer whom Obama chose to give the opening prayer at the ceremony. "We celebrate a hinge-point of history with the inauguration of our first African-American president of the United States.
"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. We know today that Dr. King and a great cloud of witnesses are shouting in heaven."
Obama put his achievement in the broader context of the American quest, ever facing new challenges, ever rising to them.
"This is the source of our confidence, the knowledge that God calls on us to shape an uncertain destiny," he said.
"This is ... why men and women and children of every race and every faith can join in celebration across this magnificent Mall, and why a man whose father less than 60 years ago might not have been served at a local restaurant can now stand before you to take a most sacred oath."
Obama warned that he took that oath "amidst gathering clouds and raging storms," and a crisis of confidence that's led to a "nagging fear that America's decline is inevitable and that the next generation must lower its sights."
He promised policies to create jobs and lay the groundwork for long-term prosperity. "The state of the economy calls for action, bold and swift, and we will act," he said.
To critics who question the scope of his plans -- more than $1 trillion to shore up banks and stimulate the economy -- he said "their memories are short. ... They have forgotten what this country has already done, what free men and women can achieve when imagination is joined to common purpose, and necessity to courage."
Earlier Tuesday, Obama opened the day with prayer.
With his family, friends and vice president-elect, Joe Biden, Obama attended a morning service at St. John's Episcopal church across Lafayette Square from the White House, his attendance marked by the pealing of a steeple bell cast by the son of Paul Revere.
Since Franklin Roosevelt in 1933, all presidents have opened their first days in office by visiting churches in the capital city. Most have gone to historic St. John's, which held its first service in 1816 and has hosted every president since then at least once during his term of office. Most sit in Pew 54, designated the President's Pew.
"In time of crisis, good men must stand up. God always sends the best men into the worst times," said Bishop T.D. Jakes, senior pastor at The Potter's House, a Dallas church, one of several ministers at the service.
"The problems are mighty and the solutions are not simple. And everywhere you turn there will be a critic waiting to attack every decision that you make. But you are all fired up, sir, and you are ready to go. And this nation goes with you. God goes with you."
The Obamas then went to the White House, greeted at the North Portico by President Bush and Laura Bush. Michelle Obama came with a gift, handing a box wrapped with red ribbon to Laura Bush. It contained a leather-bound journal and a pen to start her memoirs.
Biden and his wife, Jill, were there as well, along with Vice President Dick Cheney and his wife, Lynne. Cheney was in a wheelchair, the victim of a strained back suffered while packing for his move from the vice president's residence to a private home in Washington's Virginia suburbs.
The couples visited for nearly an hour over coffee before leaving for the Capitol. As they pulled out, moving crews rushed in to remove the Bush family's belongings and move in the Obamas', which were to be all in place by the time they'd arrive there to live hours later.
As his family settled in, Obama was to meet Tuesday afternoon with his economic team and sign some executive orders. Later Tuesday, he and Michelle Obama were to attend 10 inaugural balls.